The two selling points of the MK 5 were simplicity and "flow through" piston. Both are still valid. Modern Scubapro regulators like the diaphragm MK 17/18 are rather complex. In fact, the Scubapro diaphragm 1st stg reg with swivel turret, MK18, is the most complex first stage ever built. The piston first stages (TIS) have plastic parts which are supposed to act as "insulators" and are problematical. The second stages are crammed with O rings and tiny "balance" chambers. MY advice, if you decide to get another Scubapro, buy the MK10 or MK20 with G250 or G250HP. Be aware that the swivel turret bolt and nozzle of the MK20 are subject to factory recall. These components are soft brass and may break. However, the failures have been due mostly to incompetent technicians who over torque the parts. There is nothing wrong, really, with the MK20. The G250 is very light in the mouth and breaths wonderfully light and natural.