Looking at the Prendas website, mine seems to be the R236. Carbon, Silver, and White, but I got mine off eBay UK. The R248 is the Kompact model. My head is 55cm. I think I could have gone with a size small for a tighter fit, but wouldn't have been able to fit a skull cap or ear warmer band underneath. I have a small Giro helmet that fits like a glove, but I can fit anything on my head to keep it warm. I actually took some of the extra padding from the Giro that I didn't use and put it in the Whisper on the sides towards the rear. I think my head is more long than wide.