Ive always heard 20lbs, but never tested it myself.Always counted it as 20. But 20-25 is pretty close anyway since gym weights are far from accurate. I know the 45lb plates can be up to 3lbs off each, I even weighed some of them. Still I count it, Im not gonna weigh each plate everytime. haha =)
We have 3 different E-Z curl bars at our gym and they're all different. I just tell our members they can weigh it on our scale if they like because I can never remember. Ours are anywhere from 12 to 20 puonds, depending on which one.
I'm not sure how much our bars weigh, that's why when I use them I will write the actual weight I put on the bar with a plus sign beside it in my log book.