Only the early retro/RT/emag valves had the stepped indentation in the on-off hole. All classic/AIR valves, newer retro valves, and all X-valves have the flat bottom on the on-off hole.
Originally Posted by nak81783
The larger urethane oring holds the smaller oring in place above the on-off top. In the classic valve the small oring is teflon so that it will work with CO2. In the retro valve it is urethane. In the emag it is a buna quad oring.
Except for the Automag in front, its usually the man behind the equipment that counts.