Straight from ASV's site:
Q- What is the difference between the F1, F3 and C6 series of ASV Quad levers?
A- ASV offers three model choices in our unbreakable levers. Our newest levers, which we now call our “C6 Series” are CNC machined from 6061 Aluminum billet and carry a 6-year guarantee. Our C6 Levers have a completely new design that features “On The Fly” reach adjust! An industry first! No other off-road lever offers “On The Fly” reach adjustment via a wheel adjuster on both the clutch & brake lever. Now you can change how far your levers are from the grips anytime without tools! The levers are available in a matte finish, color anodized in Red, Blue, or Black with a laser engraved ASV logo and a new shape with a more comfortable and lighter feel. The C6 Series starts at $100.00 each.
Our "F3 Series" levers are forged from 6061 aluminum, feature a forged blade that is similar in shape to a stock lever, carry a three year guarantee and are available in anodized colors with a laser engraved ASV logo. The F3 Series starts at $75.00 each.
Our “F1 Series” levers are forged from 6061 Aluminum, have the same lever shape as the F3 Series, (similar shape as your stock levers) carry a 1-year guarantee and are our most affordable levers available starting at $50.00 each.
Our new C6 and F3 models also offer a "Pro Model" Clutch Lever and Perch that features a Pro Perch with adjust on the fly cable adjuster and other features not found on standard models. All three models are available for four strokes with integrated hot start lever options. All three models have the same folding pivot design and adjustable reach, and use the same high quality components.