I was cleaning my filter and in the process of reassembling it I broke my O-Ring. Since the pool store was closed I went to my local Ace hardware(Known as Dales' here in Fremont). They did not have a replacement but I found something else that works great! I used a pressure cooker rubber gasket which was of a very similar size( Presto 9903). Since the Pressure Cooker Gasket is flat on both sides it fitted perfectly on the collar of my Starite filter. I lubed both sides, refitted everything ran the pump and vola no leaks and a perfect fit! not bad for 10 bucks.. although you can find them cheaper on the net (6 bucks as per google)..