Hey man.
I recently ordered myself some o-rings as well, but they were for a ducky zero keyboard with mx blue switches which are quite loud by themselves.
outer diameter: 8mm /0.32inchinner diameter: 5mm /0.19inchthickness: 1,5 mm / 0.06inch
since this was my first purchase of o-rings i sadly don't have any others to compare them to, but they do their job just fine.
I ordered them from China, which took a few days (11 to be exact) but i only paid a third of the price from what caseking/keyboardjunkies asked for.
not sure if I'm allowed to post links here so here's the amazon product name: ELEGIANT 150Pcs O-Ring Switch Dampeners
if you go to German amazon (.de) and search for that you should find a review with a video aswell.