AN12 is the size you reach for when flow volume rules the design: pump suction, dry sump scavenge, oil cooler returns and big coolant runs. This straight hose end terminates PTFE hose in that size, sealing on an olive compressed onto the liner as the socket nut draws the nipple in. The straight body gives the least restriction of any hose end shape, so it is worth using wherever the routing allows. Support the hose so its weight is not hanging off the fitting, keep the cut square, and remove any burr from the liner before assembly. Only PTFE hose of matching size is suitable.