High impact plastic stacks of 16 laminated 1/16'' horseshoe shims which are adjustable to 64 different size options. Can be used to align windows, doors, curtain wall, storefront tubing and other architectural components. No waste as each stack is scored in 1/16ths, so you only snap off what you need. Length is adjustable to four sizes. Will not rot, or rust. Has an ASTM rating of 5000 PSI compression strength.