I brought a common and plus size. I measure but wasn't sure. The common size didn't fit my glasses however the plus one did. I am giving the common par to my girl friend she has smaller frames. I was surprise how the XL or plus ones are made better. The common one are all plastic where as the plus ones have rubber grips on the arms to keep from sliding off. I was planning on using a croakies but now I don't need too because of the rubber. The case is not too big and it fits in my fanny pack when not using. I think they are too big to clip on to jeans.