Strike Industries AR Lower Receiver Pro Spring Kit Black One Size. Strike Industries included the following AR15 Lower Parts in the available kits: springs for the bolt catch disconnector buffer retainer trigger hammer magazine catch selector and two detents. Replace worn springs with the Strike Industries Rifle Lower Receiver Spring Kit to ensure your weapon is functioning at its highest level. These are all commonly used springs making this bundle a necessity for any serious gunsmith or firearm owner. You never know when a spring will fail you in the field. Don't wait around for your replacement part to come in the mail. Be prepared for any malfunction or degradation of your springs by having this Strike Industries Rifle Lower Receiver Spring Kit on hand. For reference the regular kit has one of each spring and two detents. The pro version has 20 of each spring and 40 detents. COMPATIBILITY: Mil-Spec AR-15 and typically most AR-10 lower receivers Specifications for Strike Industries AR Lower Receiver Spring Kit: Manufacturer: Strike Industries Color: Black Finish: Matte Gun Make: AR Platform Gun Model: AR-10 Features of Strike Industries AR Lower Receiver Spring Kit Optional 20 piece gunsmith box also available Replace worn springs Commonly used springs Essential for a gunsmith or AR owner Package Contents: Strike Industries AR Lower Receiver Spring Kit 1 x Bolt Catch Spring 1 x Buffer Retainer Spring 1 x Trigger Spring 1 x Hammer Spring 1 x Disconnector Spring 1 x Magazine Catch Spring 1 x Selector Spring 2 x Detent Spring Strike Industries SI-AR-LRSK-PRO: AR Lower Receiver Pro Spring Kit Black One Size