This cheek piece set will raise your eye level 1.4 cm or 2.6 cm for proper sight or optic alignment No gunsmith or tools required, the cheek piece installs instantly on most ribbed collapsible M4-style stocks simply by snapping into place and is ideal with #CBS buttstock. CP1 will raise your eye level 1.4 cm. It weighs a negligible 50 gr. and measures 9.7 cm long x 5.4 cm wide. CP2 raises 2.6 cm, weighs a 56 gr., and measures 6.5 cm long x 13.1 cm tall. They are Mil-standard, made of a rugged glass-reinforced polymer to withstand harsh tactical conditions.