how to tell if Rt has two o-rings

[blakdragon21]

how can you tell if the retro vavle has 2 o-rings to accept the ult?

[abaez]

Take your on/off out and look inside.. if you see two o-rings in there thats it. It should be one large one with a smaller one in the middle of it (the smaller one might come out when you pull the on/off)

[trxtr]

I thought all Retros had 1 o-ring (except newer RT-Pros). I may be mis-informed.