These CRL Plastic Bearing Shimstrips are intended for use in placing and leveling curtainwall and storefront metal in concrete openings. They are made of an extremely strong multipolymer plastic that withstands tremendous loads without compressing or deteriorating due to chemicals, moisture or rust. These solid shims can be drilled in the center to allow placement over the bolt which prevents the shim from possibly moving, as can happen with horseshoe shims with slots. The 4" x 2" (102 x 51 mm) shims snap from the factory strip, and are available in thicknesses of 1/4", 1/8", and 1/16" (6.3, 3.2, and 1.6 mm).