SLP's line of drive springs allows you to choose a spring that not only gives you the engagement that you desire, but also delivers proper peak RPM. Made using only the highest quality Chrome-Silicon wire that has been shot peened to make a very durable spring that is resistant to sag and breakage. This green with pink stripe spring SLP 40-77 is a recommended component in many of SLP's clutch setups and has the following spring rates: Arctic Cat: 150 / 330 (Measured in pounds at 2 9/16" and 1 5/16") Polaris: 160 / 340 (Measured in pounds at 2.50" and 1.25") Some specialized tools are highly recommended for the installation of this SLP primary spring: -Primary Clutch Holding Tool 20-202 (holds primary clutch from turning while removing or installing the clutch on the tapered shaft) -Primary Clutch Puller 20-136 (removes the primary clutch from the tapered crankshaft) -Clutch Press Tool 20-222 (compresses primary or secondary clutch for ease of dis-assembly and re-assembly when under spring tension)