JP Enterprises AR15/M16 Alternate Spring 5-Pack Features The AR15/M16 Alternate Spring 5-Pack provides five distinct spring rates identified by color coding on one side of each spring allowing for fast visual identification during installation and swaps in the field or at the bench. If the buffer head is felt to fully compress and bottom out during firing a heavier spring from the kit should be selected to slow bolt carrier velocity and prevent bottoming out while shooters experiencing unreliable bolt hold-open on the last round should move to a lighter spring to allow the bolt carrier to travel rearward with sufficient velocity to engage the bolt catch. The color coding system with white black green yellow and no color identifying each of the five spring rates eliminates guesswork and simplifies the tuning process during live-fire testing and adjustment. An important consideration when selecting the appropriate spring rate is the presence of an ambidextrous bolt catch extension such as the Magpul BAD lever as the additional mass on the bolt catch combined with the higher bolt carrier velocity produced by the JP Enterprises Silent Captured Spring system with a heavier spring can cause the bolt to override the catch before it engages on the last round. In this case a lighter spring from the AR15/M16 Alternate Spring 5-Pack will typically resolve the issue without requiring removal of the ambidextrous component. The included spare guide rod retainer screw is a practical addition that provides a ready replacement in the event of thread stripping during Silent Captured Spring disassembly and reassembly. JP Enterprises AR15/M16 Alternate Spring 5-Pack Specifications Manufacturer: JP Enterprises Model: AR15/M16 Alternate Spring 5-Pack Compatible System: JP Silent Captured Spring Platform: AR-15/M16 Springs Included: 5 Spring Identification: White Black Green Yellow No Color Includes: 1 Spare Guide Rod Retainer Screw