Diamondhead VRS Long Rail (Single) (M4/AR15/M16) Fits all M4/AR15/M16 variants Rail & Bumper Kits include hex screws & Allen key Mil. Spec. Type III anodized 6061 T6 aluminum construction & Mil. Std. 1913 Picatinny rail dimensions Mix full length & short rails with bumpers; Add more rails as additional accessories are needed Fast configuration changes; Combat durable