B5 System's Have Developed the Next Evolution for the Drop-In Style Handguards The B5 Systems AR-15 M-LOK hand guard features a slim design with outstanding grip and control. This polymer hand guard features one of the narrowest drop in systems available on the market today. This particular version incorporates Magpul M-LOK modular attachment system. M-LOK accessories are easily mounted to the hand guard without needs to remove the hand guard. The hand guard is made from a durable composite polymer construction with a built in stamped metal heat shield.