In 2012" RS Regulate began rolling out the first models of the AK-300 Modular Side Mount System, which now features six fully modular uppers and nine different lowers: a front-biased, a rear-biased, and a full-length lower for most Eastern European AK side rails; a front-biased and full-length lower for Yugo/Serbian rifles; a PSL and and Romanian M10/RH10 rifles; a Century Arms proprietary side rail; and even a rear-biased lower for Czech vz. 58s.Features : Yugo Front-Biased Lower Common Usage: Yugo/Serbian Type Rifles (OPAP, NPAP or M21 pattern rifles) Product Dimensions: 5.71 x 0.55 x 1.88 inches Weight: 3.37 oz