Thank you Mr. X. From checking size charts (but yes not totally reliable!) it looks like maybe you just went one size up, which sounds like you do for boots. I think I should be a 41/42 (and I've had shoes in this size but I may have even fit a 43, as you say it's very tricky!) I'm usually a 10.5 or 11 in women's US, and 9 or 9.5 in mens. So maybe the 43/44 fins would be good if I want to wear 5mm, but maybe I'll only need 3mm, since as you say the fin pocket also provides warmth. All so annoying. I'll just have to buy and try and maybe have to send back for exchange.