I can't fit into Giro or Bell--I'm between a small and medium. Small barely fits, and I can't get any caps under. A medium is too big.

Specialized helmets fit me best. I used to have an Aurora (cheaper version of the Decibel). Now I use a Propero (cheaper version of the S-works 2D). I like the S-works too, but the straps are too close to the backs of my ears and feel weird. The Propero is lighter and more ventilated, and the retention system doesn't hit pressure points in the back like the Aurora used to. I find it's also a little more sunglasses friendly, because the retention system doesn't come down so far where the arms of the glasses go. Plus, it's over $100 cheaper than the S-works. I do really really like the white/navy S-works for color, though, because it would look great with my kit.