The helix lives within the secondary clutch. The helix helps apply pressure to the CVT drive belt.There are two types of helixes, straight and progressive.Straight helixes will have the same angle cut the whole duration. A progressive helix with have two different cutsfor different shift points.Different helixes with more aggressive or less aggressive angles can adjust the pressure on the beltand shift points.If you get too aggressive with thehelixangle, anddon'tadjust the secondary spring you will cause belt slip.Ifyour rpms are too low, a shallower rangehelixand/or stiffer secondary spring will raise rpm. This will alsoprovidemore squeeze on the belt which is useful if you are experiencing belt slip. Conversely, if your rpms are too high, a steeper rangehelixand/or softer secondary spring will lower rpm.