My first size was an A24 Finding the correct size is not easy . This inner wear was too tight , was never able to get it on , and ended up removing the silicone end ring . The strap is also way too tight and the snaps dig in ( maybe an option of snap/no snap . I have never used the snaps or maybe make the loop one size with snaps to adjust the size, just a though. I then ordered an A28 . This was better, I was able to get it on but the A28 band was too loose and had issue using the facilities. I next ordered a A30 , the fit was more comfortable but the head ring was too big and I would slip out of the device . My last order was a B28 . I thought the length would help stretch me all day but the fit was way to tight and its very difficult to get on . I don’t understand why its not the same size as the A28 in girth , it fit more like the A24. What I end up using is the A28 with the A24 band . Even a smaller band would help from slipping though and I always remove the band when using the facilities . I probably have more issues than most here because I am post prostate cancer surgery .