When I resurfaced my inground spa last year, I removed the 10 spa jets (model # 210-6090 3-3/8" size). These units have black o rings in the back of the jet that I want to replace. Can anyone advise where to find these o rings? To replace jets, cost around $30 each. I feel o rings are worn (14 yrs old) and should be much cheaper. My guess is the o rings help separate the air and water. Air flow seems to be less than b 4 I did the resurface work.