The AR15 Master Bench Block holds 5 key AR15 components in 8 different orientations to allow you to knock out and install up to 13 different pins. The block is wrapped in over-molding that grips your bench so it wont slide around. Clear. engraved labels tell you what component fits where. and what size punch youll need to knock out the pins. The biggest innovation is mounted inside four strong magnets immediately grasp any pin you punch out and hold it securely to the block. It even includes storage for common size pins. This is a bench block you can swear by.