SAM B Waterproof uses series codes for their products. B1 is the first generation, B2 the second. The B1 is listed as a semi-dry boot, fin strap ridge, lined and a few other differences. The B2 is slightly more basic. The best thing is to go to the manufactures website and compare the two. I have quite a bit of gear from Waterproof and love it! Very high quality. However I did return the B2 boots I ordered because they were too large.. I wear a 10 (in most brands) I ordered the L (9-10) and was a size to a size and a half too large. Everything Else (suit, gloves, hood) are true to size. Also, LeisurePro did not send me a smaller size as asked, they refunded the purchase to my card...