The Stealth Recoil Spring comes with Red LOCTITE on the front metal stop and Blue LOCTITE for the bottom bumper. It is always a good idea to tighten the bumper screw and cap before installation and re-tighten for regular maintenance. If reassembling we recommend re-applying LOCTITE. The Stealth recoil spring can be installed with or without a buffer retainer. The polymer bumper goes towards the rear of the firearm and the weight mass with the o-ring goes towards the bolt carrier. (9mm Bolt Carriers ONLY)For proper function of the SRS-9 in your 9mm rifle or pistol, the extra weight on the back of the bolt carrier needs to be removed. It is held in with a spring pin. Most bolt carriers have a rear opening of over .60″, there are a couple of bolt carriers in the market place that have a rear opening of under .60″ and will not function with the SRS-9.