The Intrafuse AR15 stock wrench is a must for assembling/disassembling your AR15. It has 3 core wrenches in one: Mil-Spec castle nut, receiver extension removal, and A1/A2 Flash Suppressor. The added rubber grip gives you further comfort and grip while working on your AR15. The material its made out of is a heat treated steel that is coated with a manganese finish to help protect from rusting.