The spr3 rail system features a full length picatinny rail, front and ear qd sling attachments and a flat bottom rail that offers a stable shooting platform.It is a free-float design.This model features m-lok slots.*note- this model is not compatible with the ruger precision rifle without purchasing the ruger mounting nut and is not ar10 platform compatible.Rails: Picatinny/M-LOKFirearm Model: AR-15Material: 6061-T6 AluminumFinish: Black Matte AnodizedFree Floating: Yes