Another side note....
NOT to hijack the thread, but....
Some of you mentioned "Adel" clamps. I use these types of clamps in my manufacturing business, to the tune of about 5,000 of them per year in a 2.5-inch I.D. / size. When researching places to acquire these clamps, I quickly learned that 'Adel' is a trade name, and not the real and/or the only descriptor for the clamp. Same thing as calling a tissue a Kleenex, or a soda pop a Coke. In other words, the Adel company was the first to make them and the name kind of stuck.
If you need a GREAT source for Adel-type clamps, do a quick Google seach for Umpco, Inc. They are fantastic to deal with, will sell in small quantities, and their prices can't be beat- even on small ticket orders. In addition- and back to the thread topic- McMaster is a great source for your washers. Don't ask me how they do it, and don't even charge for it, but: if you order something today, you always get it tomorrow with NO overnight fee's. I ordered about $20 worth of plastic hole plugs from them on my first order, and low and behold, the next day a courier brought them to my office! Incredible service! And, they will also give you a catalog that honest to God, has everything in it you could ever think of, and weighs about 15-pounds!
Hope this helps someone along the way...