Now since you were talking about replacing the O-rings on your Excalibur, you got me thinking. It's already been around 8 years since I replaced mine, so I took the whole thing apart to check the insulation on the wires, and O,-rings. I have a stainless dental pick I use to remove the top ones. They were still good, as well as the two inside as I was surprised as it's been a while. Taking them out damaged them, so I ordered some new ones for the top. The best I guess are the Nitrile ones, because of the shaft movement. Make sure you use a top grade silicone grease (divers grade, or similar), when replacing them. The dimensions for the ones on the top are 8mm OD, 5MM ID, with a thickness of 1.5mm, in case any one is wondering.