Cole-Tac Backbone Bag Frame ARCA Square Black. The patented design eliminates the need for straps that attach the support bag over the rifle or optic. The hard-coat anodized frame attaches to the rifle by either an American Defense Picatinny mount or an Area 419 Arcalock mount. Four Hook and Loop straps keep the bags securely in place and the wide surface area of the frame prevents the bags from twisting and shifting. Specifications for Cole-Tac Backbone Bag Frame: Manufacturer: Cole-Tac Fabric/Material: Metal COLETAC BF1003 BACKBONE FRAME ARCA SQUARE Cole-Tac BF1003: Backbone Bag Frame ARCA Square Black