Use the Gray Ops CNC M-Lok Rail Weight Set to get the perfect balance with External forend weights. Designed for M-Lok chassis with configurations similar to the MPA Matrix.Features Integral Flush cupCompatible with M-Lok mounting systems Shaped to be support hand friendly during push/pull/press positional shootingCompatible with MPA internal weight kits on MatrixFull kit (6 weights) includes 4 short weights and 2 long weightsFull kit adds just over 2.5 pounds (41 oz.)Short Weights- 3.125" in length at 6 oz. each (Covers 2 M-Lok slots)Long Weights- 4.7" in length at 9 oz. each (Covers 3 M-Lok slots)