The super modular rail (smr) mk8 m-lok is geissele's ultra-modular model.It is designed to give the user full modularity while maintaining a strong and rigid platform.Maximum venting at the lower 45 degree quadrants create maximum heat dissipation and also dramatically reduces the rail's overall weight.The rail utilizes magpul's m-lok technology at the 3 6 and 9 o'clock positions as well as the upper 45 degree quadrants.The smr mk8 is both versatile and modular allowing the user to tailor their platform to his or her unique needs.Note: this rail is designed to work with mil-spec m4 upper receivers.The compatibility with billet receiver sets is unknown.Rails: PicatinnyType: Railed ForendFirearm Type: RifleFirearm Model: AR-15/M16/M4Material: 6061-T6 AluminumFinish: Anodized