The EGW chamber checker is ideal for reloaders or shooters who want to ensure that ammunition is not too tight or loose to fit in their chamber. These blocks are machined from solid blocks of 6061 T6 aircraft grade aluminum and anodized in a long lasting black finish. EGW uses the same chamber reamers that are used by gunsmiths and barrel makers when machining these blocks so you know if your ammo fits in the block it will fit in your chamber. Just drop loaded rounds in the chamber checker, if the round is flush with the top of the block it will fit in the guns chamber.