The Magpul ACS (Adaptable Carbine/Storage) – Commercial-Spec model is a drop-in replacement buttstock for AR15/M4 carbines using Commercial-Spec sized receiver extension
The Magpul ACS (Adaptable Carbine/Storage) – Mil-Spec model is a drop-in replacement buttstock for AR15/M4 carbines using Mil-Spec sized receiver extension