Castelli Summer Skullcap
This is that perfect cap to wear under your helmet in the summer. Mesh on the top allows for lots of airflow, while the velocity fabric around the base absorbs moisture to keep it out of your eyes.
I've tried various headbands and skull caps to help with the sweat getting in my eyes. The Castelli cap has been the ticket! So comfortable you don't even know it's on. And I haven't had any issues with sweat. I wear it year round and it breathes well no matter what the season is. Definitely check this out. I'd give it more than 5 stars if I could.