CRL Shimstack Shims give you fast, low cost leveling. 16 heat-sealed pieces make up each one-inch stack. Simply snap off individual shims to get the thickness you need. With so many available sizes, Shimstack Shims can be used to align windows, doors, curtainwalls, storefront tubing and other architectural components. Each pack contains 1000 pieces. The convenient installation tab allows the shim to be easily inserted completely within the gap, and can be easily broken off after insertion. Shimstacks are made of black fire resistant, non-staining, high-impact plastic with an ASTM rating of 5000 p.s.i. compressive strength.