My top was leaking most of last year and someone previously had tried to silicone it so I knew it needed replacement. I didn't mind the price of the O ring but the spanner tool P/N S200KT was four times the O rings cost. Normally I love to buy tools but I don't think I'll be doing this again. I ran across a Culligan water filter housing wrench P/N SW-3A at Fleet Farm and wondered. It was only five something so I bought it and amazingly enough it works. It only has six "cleats" where the dome has twelve but they engage properly and I was able to spin the top off so I can clean it up and reseal it with the new O ring properly.