HLO Extraction rack bolts are designed specifically for our rack mounted systems. The rack bolt allows the pipe hangers to be connected to the rack easily and efficiently. The bolt is a 1/2" BSP which allows heavy parts to be held using the pipe hangers. The box section of the bolts 4" x 4" which fit perfectly onto the HLO extraction racks. Over time the 1/2" threads can become damaged so its advisable to have spares on hand.