Store an additional 2 rounds on the side of a rifle with the MDT M-LOK Multi-Caliber Spare Round Holder. Wide range of round compatibility including .223 300 AAC .224 Valkyrie 7.62×39 6.5 Grendel .308 6.5 Creedmoor 450 Bushmaster 7mm 300 WM 300 PRC 6.5 PRC and more. Includes a small and large caliber polymer body with adjustable spacer system for maximum compatibility. The spacer system uses Mil Spec washers and O-Rings to offer the perfect fit. The holder can be mounted using M-LOK or the accessory holes on the side of ACC chassis. The reversible design allows for mounting on left or right side of chassis.