What to look for in a post pump cock ring?

Depends on why you want/need a cock ring. If you have high EQ and just want to maintain that extra engorgement, the stretchy silicone rings would be a good idea. If you lose a bit of EQ after a pumping session, a nice beaded cock ring or a neoprene cock ring (a little stiffer than silicone) works well. Got a little ED or want to increase hardness? A properly sized rubber O ring or metal (more expensive) cock ring is in order. If you have a severe case of ED, nothing works better than an Osbon tension band.

dtwarren1942 What is the difference between an Osbon tension band and one of those conventional silicone cock rings? Also will they work with most pump cylinders or do you need to buy a special Osbon one?