Frequently Asked Questions


  • Flexible Line Blades fit to its own special head, and cap assembly. Hardware is available to allow easy fit to over 99% of all gas trimmers.
  • The Patented AERO-FLEX® system replaces current unreliable, monofilament cutting line systems, brittle plastic blades, and some metal bladed applications often utilized with handheld grass trimmers and brushcutters
  • Easy Reloading – In a snap
  • Efficient, streamlined, and powerful trimming operation
  • They are aerodynamically streamlined for low drag which saves power
  • The nylon line blades have a flexible impact hinge (very durable and reliable)
  • They are very powerful and strong
  • Makes your trimming job a more pleasant experience. You can operate very efficiently at very low RPM’s.
  • The bright reflective orange & yellow colors create a visible cutting swath (under most light conditions) enabling the operator to observe and utilize it for additional control as you feed the trimmer into real sensitive areas. This feature is not available with conventional round line which operates with an invisible swath.

The causative reasons for such repetitive failures are the needed high speeds required to drive conventional monofilament line. High speed creates extreme stress to the already weak line itself causing it to easily break. Additionally, their feeding systems are very unreliable and complex to reload. These combination problems create constant harassing interruptions causing the operator to constantly stop the trimming job for repairs and line replenishment. Monofilament line doesn’t cut well, is cumbersome and inefficient. It easily rips or breaks out against a fence. It’s noisy and creates uncomfortable vibration.

But now, Aero-Flex®Technologies, Inc. has the scientifically engineered solution.

The problem is substantially reduced with the AERO-FLEX® flexible, impact absorbing line blade system that is scientifically engineered to reduce operating stresses that cause the failures thus dramatically reducing down time. High RPM’s are the major contributing culprit combined with the weak monofilament line that inherently needs high speed to generate itself as a vegetation cutting member. Repeated impacts to the thin line cause rapid fatigue and overstress resulting in a continuous breakage/replenishment process. If you slow it down it doesn’t cut well.

High impact forces from high line speeds against hard abrasive surfaces that create abrasion wear or overstress/breakage at the outlet, the cutting tip or internally within the spool. Further, monofilament line will snap off when rapidly impacting against abrupt obstacles it can’t cut. The line itself overstresses and pulls out as it wraps like a “zoro” whip around an obstacle such as a fence. It breaks off at the eyelet or inside the spool. Many times it welds internally (ultrasonic welding) binding it from feeding out again. Frequently, due to moisture loss from the nylon, it becomes brittle. Nylon requires moisture. When it dries out in the dryer climates, it easily breaks.

Our Philosophy: Slow it down, beef it up and make it easy! You’ll experience the pleasure to get the job done easier, faster, more efficiently, and with much better cutting quality. When the line blades wear out reloading is simple and easy. The lines are strong. Powerful AERO-FLEX® Line Blades are capable of cutting at low speeds. They cut better and faster even for edging, trimming, and even some bushhogging.

Unlike conventional lines, AERO-FLEX® line blades cut very well at lower speeds against abrasive surfaces. They do not need high RPM’s which creates more rapid wear. The slower they go, the longer their life. The type of abrasive surface also makes a difference such as against asphalt, concrete, or wood. The slower you go against these surfaces, the longer line blade life thus enabling you to maximize the benefits of the AERO-FLEX® system. Achieve lower RPM’s by using part throttle or at reduced engine power.

Comparative abrasion testing with an equivalent length of AERO-FLEX® line blades will outlast round line while at high speeds by at least 20:1. Round line cannot cut at very low RPM’s, but AERO-FLEX® line blades will continue to cut and will operate 50x farther (without stopping) against the most abrasive surfaces until there is need for replacement. This is accomplished by operating at part throttle. In heavy vegetation, round line snags and pulls out of the head where as AERO-FLEX® line blades keep on going and impressively demonstrates an incredible capability to slice into heavier vegetation. Under these rough impact conditions, AERO-FLEX® line blades will eventually reach a fatigue limit and break, thus needing replacement.

Yes! Conventional line against a wood or wire fence is a recipe for immediate failure. AERO-FLEX® line blades are more easily controlled at lower RPM’s up to a fence. Its visible swath allows you to avoid hitting the fence. When and if the lines hit and contact the fence they more easily slide off and do not wrap as commonly occurs with round line. Therefore, AERO-FLEX® line blades will survive a fence but continued heavy impacts will eventually cause them to erode and stretch. We strongly recommend as you cut up against such obstacles to operate at much lower RPM’s but sufficiently elevated to where the vegetation can be cut.

Low drag returns you more power for more useful work and efficiency rather than wasting valuable energy. The AERO-FLEX® line blade is shaped like a teardrop. It is designed to run through the air like an airplane wing. It streamlines the airflow across its surface. Air drag is composed of both friction and a vacuum pull from the trailing side. The AERO-FLEX® line blade teardrop profile substantially reduces these drag forces. There is also a major reduction in grass drag with AERO-FLEX® line blades compared to round line which folds back and drags along the grass. AERO-FLEX® line blades hold a stiff and straight cutting blade structure which substantially reduces grass drag. Therefore, the combination of both air and grass drag can amount to a substantial power saving almost enabling most trimmer engines to now complete the job with about 1/2 of its original power thanks to the efficiency of the AERO-FLEX® System.

When trimming with reduced speeds at part throttle, more than half the fuel normally used with round line can be saved. This not only saves fueling time but allows you to continue to trim with fewer interruptions. Your time is valuable. AERO-FLEX® systems save time and money.

There is substantially more kinetic energy associated with the higher mass and speeds and the greater number of AERO-FLEX® line blades. In addition, since the leading edge of the AERO-FLEX® blade is sharper than its equivalent round, the higher kinetic energy will be transferred to the vegetation through a more concentrated and sharper leading edge. This breaks down heavy vegetation easier. AERO-FLEX® line blades will cut heavier vegetation than round lines can. In fact, AERO-FLEX® line blades may be capable of cutting some heavy vegetation normally requiring the use of metal blades but will not cut woody brush. Cutting such heavy vegetation with heavy impediments (occasional brush) is very fatiguing to the line blades. You may have to consume several sets of line blades to get the job done.

Installation Questions

AERO-FLEX® trimming systems will fit virtually all gas but rarely some electric trimmers on the market. A full array of components are available to select the proper parts for your trimmer. The degree of difficulty in conversion is relatively simple especially when you follow the detailed directions provided by Aero-Flex® Technologies, Inc.

Detailed instructions are provided for the various types of trimmers that exist on the market. The entire head of your old system has to be removed and replaced by the AERO-FLEX® head. There are trimmers with long arbors and short arbors provided by the various trimmer manufacturers. Once you determine the system you have it is simple to follow the directions and to remove the old system for “upgrade” to AERO-FLEX® System. If your system is unusual you can call us for help (888-880-2376) and for special instructions. We will make every reasonable effort to custom fit your trimmer or help you through the process of conversion.

Most trimmers can be easily converted back to their old systems with the exception of the ‘yellowish’ MTD or the prior Ryobi “speed spool”. Be sure to save the parts from the old system. However, if you have learned to operate under the conditions in which the AERO-FLEX® line blades were designed and use them as recommended, we believe you will truly appreciate the performance advantage provided by the AERO-FLEX® trimming system.

No, the AERO-FLEX® head is designed for AERO-FLEX® line blades. Once you experience the benefits of AERO-FLEX® line blades you will more likely no longer care to use round line.

Operating Questions

There are some trimmer heads that turn clockwise and some turn counterclockwise. For maximum aerodynamic efficiency, the rounded edge of AERO-FLEX® line blade leads into the cut so as to gain the low drag aerodynamic advantage. Orange line blades are for counterclockwise while yellow are for clockwise rotation and they are intended to cut on the leading blunt side to best realize the scientific streamlining. The specific colors of orange and yellow were selected because they are most capable of reflecting light back to the operator. This provides a helpful control when you can see the visible line blade plane. There may be a harmless initial noise that will go away. Trim at lower RPM’s. Use part throttle or part trigger. When you want to slice heavy vegetation, use full throttle.

Yes, we recommend you start off with 2 orange and 2 yellow. Don’t worry about direction of rotation. You will begin to experience the benefits of AERO-FLEX® line blades. Then as you become more familiar with them you can adjust and select to your preference. For general cutting with a slight helpful updraft and a cleaner cutting quality you can use 2 orange and 2 yellow, alternately mounted. It makes no difference if your trimmer turns clockwise or counterclockwise.

Yes, with the same colors mounted opposite each other, will create 2 lines leading with the sharp side at a downward pitch while 2 will lead with the blunt side with an upward pitch. The result is a fairly aggressive cutting action with a helpful updraft that helps lift grass into the cutters for a clean, precise cut. There will also be less grass browning.

Yes! If you’re looking for maximum aerodynamic efficiency and downdraft for blowing debris, then use 4 orange on counterclockwise rotating trimmers or use 4 yellow on clockwise rotating trimmers.

While we recommend a leading round edge for trimming (which captures the many efficiencies), there is a way (see Chart below) to select the sharp edge which requires a specialized cutting technique. However, you should be aware of the advantages and disadvantages of each choice.

  • Round side cutting offers the best in drag reduction, lower noise, downdraft air for blowing away debris, tends to throw more objects downward, and higher energies for cutting heavier vegetation. Use all 4 orange for counterclockwise and all 4 yellow for clockwise rotation
  • Sharp side cutting offers a very clean, high quality cut on finer grass (to reduce grass “browning”). The updraft will pull grass up (like rotary mower) while it is being cut. It will lose its quietness and lower drag features when the intended airfoil is run in reverse. Use all 4 yellow for counterclockwise and all 4 orange for clockwise rotation

Yes! 4 line blades are highly recommended but, 2 line blades can be used for very light trimming or if your trimmer’s engine appears to be too weak for 4 AERO-FLEX® lines. Using 4 line blades will allow lower speeds against abrasives thus increasing their useful life. Also 4 line blades have some power and cut heavier vegetation better.

More likely most gas trimmers become overpowered with the power saving created by the efficient AERO-FLEX® Line Blades. This is why we stress that you use part throttle and operate at lower RPM levels especially against hard, abrasive objects. Since such high power is not required, we expect trimmers to become much smaller and lighter with the added benefits resulting from the Aero-Flex® Technology.

Yes! Low RPM trimming was a AERO-FLEX® system design goal. It is a beneficial technique and makes good sense to reduce speed. Conventional lines cannot cut at the advantageous lower speed levels of AERO-FLEX® Line Blades which function over a much wider speed range from idle to full speed. Lower speeds make sense, they reduce complexity, dynamic forces and resulting stress to the line blades and also to the trimmer itself. Conventional line must be revved up to much higher speeds to cut where it creates these highly destructive stressing impact forces while requiring high power to drive through natural air and grass drag resistance.

Most trimmers on the market will easily drive four AERO-FLEX® line blades. It takes a learning experience and technique. On some lower power trimmers (w/o clutch) an abrupt entry into the cut with the stronger line blades will cause the engine to stall. Avoid rapid overfeeding the strong line blades into heavier grass or into the ground which could cause the engine to stall. Develop a technique to gently feed the side of the rotating line blade plane into the vegetation. Don’t cut on the “spoke”. Don’t “hack” back and forth! Your trimmer may have its own engine difficulties where it may have lost power or its carburetor is not adjusted properly. You may want to operate with only 2 line blades to relieve the torque feedback to prevent engine stalling.

Yes, unless you are using 2 orange or 2 yellow, high downward air (from higher speeds) may have an effect on certain light grasses. When running too fast there will be some fast moving air blowing downward that may push the grass aside, making some believe the leading round part of the cutter is not cutting the grass. Recommendation: Run slower by using part throttle, there will be very little air moving downward to push the grass to the side. Rest the head on the ground and gently slide it into the grass to be cut, using the outer edge of the swath. You will also benefit with a substantial fuel saving, a much quieter operation, more control, and a more pleasant trimming operation.

Very unlikely. In fact, lower speed is better. Essentially, light trimming at part throttle reduces the adverse stress effects on the engine itself that are created by high RPM’s. A low speed trimming operation is also much more pleasant with reduced noise, vibration and thrown objects. While each engine may behave differently, it is recommended that occasionally you rev the engine to clear any residual fuel from the internal engine and muffler and continue to revert back to a slower RPM operation. As a further suggestion, many engines, whether run at low or high speeds may begin to experience exhaust screen clogging which tends to choke the needed air flow through the engine. Follow directions in your trimmer’s operator manual. Remove the screen, clean and replace it. You’ll see how much better the engine will operate. Always use the oil/fuel ratios recommended by your trimmer’s manufacturer. Don’t use excess oil, it will clog the screen faster (More is not better). Rarely, some engines may experience vapor locking as the effect of its cooling air flow may drop at the lower speeds. Vapor locking can be recognized by engine stalling and hard starting when hot. Don’t use older fuel – always use fresh gas. Certain engine systems may not allow real low operating speeds because they may not have the capability of adequately cooling its fuel system.