Tactical Solutions X-Ring Bolt and Recoil System Maintenance Kit. The included items are suitable for both current and previous bolt design generations. If your bolt features an engraved Z on the lower left-hand side utilize the longer 1/2 inch Firing Pin Stop Pin. If your bolt lacks the engraved Z opt for the 3/8 inch Firing Pin Stop Pin. Specifications for Tactical Solutions X-Ring Maintenance Kit: Manufacturer: Tactical Solutions Gun Model: Tactical Solutions X-Ring Fabric/Material: Metal Action Type: Bolt Action Package Contents: Tactical Solutions X-Ring Maintenance Kit 1 Plug O-Ring 1 Firing Stop Pin 1 Firing Pin Spring 1 Extractor Spring 2 Recoil Springs 1 Buffer 1 Extractor 1 Extractor Plunger 1 Firing Pin 1 (Gen 1) Firing Stop Pin What firearm models does the manufacturer say Tactical Solutions X-Ring Maintenance Kit is compatible with? The manufacturer says that Tactical Solutions X-Ring Maintenance Kit is compatible with Tactical Solutions X-RingTactical Solutions XR2-MAINT: X-Ring Bolt and Recoil System Maintenance Kit