Machined from 6061 T6 aluminum and hard anodized, this A3 Industries rear stock/brace adapter replaces the original end plate on your MP5K and clones. The adapter allows the use of A3's modular line of stocks and braces using the 1913 Picatinny rail. FeaturesMachined from 6061 T6 aluminumType II anodizedNo modifications to firearm needed NOTE: HK's and clones have two different rear ends, a single-pin design and a dual-pin design. The K-models and some hybrids use this dual-pin design.