TacMark QTY 3 Rails KeyMod Picatinny Accessory Set TacMark product - QTY 3 Rails KeyMod Picatinny Accessory Rail Set 1x 4.5" 8 Slots, 2x 3.35" 5-slot KeyMod Picatinny Accessory rail, mounts onto KeyMod Spec. handguards. Black Anodized Aluminum Construction