The Hogue Freedom Fighter AR-15 Fixed Magazine Refill Kit is used in conjunction with the main Freedom Fighter Conversion Kit. Since the original kit has the installation jig and drill bits needed to modify an AR-15 rifle, you only need the "consumable" parts - the pin and spring assemblies - to convert additional rifles. Hogue set up the Freedom Fighter AR-15 Fixed Magazine Refill Kit so you can modify additional lower receivers or replace lost/damaged parts on already-converted rifles without spending money on tools you already have.