Mother Clutcher brand primary and secondary clutches and primary puller tool for 2015 RZR 900 and 2015 RZR 900-S. Nothing needs to be done to them before being installed! Both come ready to bolt on and ride with spring and weights already in the primary and the spring and helix already in secondary! The primary in this set is original style and stock tuning besides spring is a upgrade on engagement. It gets rid of choppy/ jerky engagement issues that some years of the oem primary clutch had.The secondary is the tied style like came stock on 2016 +models but has the 2015 splines in it to be a bolt on upgrade on the secondary clutch. This secondary gets rid of the problematic Rapid Reaction secondary. The secondary clutch not only is a tied style upgrade but also comes with the round rollers instead of the problematic "square pucks" the first time so you can get long life from your new secondary clutch. Another benefit of upgrading to tied style secondary is longer belt life.