So, I'm in need of a crank puller and need to know what size to buy. I have an SR Apex crankset from the late 70's. I would assume they're just the standard 22mm size but would like to be sure before I purchase. I really don't have a way to measure them.

Edit: I'm also having trouble removing one of the dustcaps. The driveside cap screwed off with ease but I'm having quite a time trying to get the other one off. They're just plastic so I really would like to avoid destroying them if possible but may have to anyway and replace them eventually.