Sig Sauer Tread Vertical Foregrip with Barricade Stop, M-LOK, Fits AR-15 Rifles, Black KIT-TRD-GRIP-VERTICAL-BLK The Sig Sauer Tread Vertical Foregrip with Barricade Stop is a factory replacement M-LOK vertical grip for the M400 Tread rifle series. The dual angle vertical grip comes with included M-LOK connectors and mounting hardware.