With the exception of some winter gloves, I've found Castelli apparel consistently sized way too small and ill-fitting. For that reason I was skeptical of the "one-size-fits-all" description for this cap, but I gave it a try with the hope it would provide lightweight and breathable head cover under my helmet in cold and damp weather. It is well-constructed with quality materials, I'll give that. But as with so many Castelli pieces of kit, this only fits smaller heads because the trimming along the hem has no elasticity, no stretch whatever. The circumference of my skull is ~59cm, which straddles medium and large helmet sizes, but this cap barely fits and is so tight that it gives me a headache after a while. How is this "one-size-fits-all" if there is no stretch to accommodate different head sizes? Unless you have a smaller pate, save your money. It won't fit.
So, I'm nearly bald. That makes keeping my head warm more of a challenge riding bicycle when the temps are in the 20's -30's.and the wind is gusting to 30mph. I've tried several options and I'm either too hot or too cold. The Castelli Difesa 2 Cap does have a down side, and that's it's size. It fits small at first. I remedied this by stretching the cap out quite aggressively without damaging it. This worked! It's now even comfortable with a thin skull cap underneath. As a reference, my normal hat size is 6-7/8, to 7. I'm glad I bought this cap. It makes all the difference.
Love this, fits great not bulky and really does what it says it will do. Far warmer than expected and because it sheds rather than absorbs moisture, it stays warmer than even a wool cap. Wearing it on every ride this winter. Brim keeps its shape and yep, keeps at least some of the rain off glasses.
Wind was blowing...Snow coming down. Great conditions to road ride test with the new Castelli cap. Perfect....Kept my ears warm, brim kept some flurries outta my face. Cap is Windstopper, the ear flap is not. But it's thin enough that you can wear under your helmet, and the ear flap is thick enough that it works keeping your ears warm, plus you gotta be able to hear, right? It's a little pricey but Castelli stuff is usually top quality. If its brutal cold (Hello Minnesota) this thing may not be enough but for anything in the 10s to 30s it's my new favorite headwear.