Use it only on the hotest most humid days riding in the blazing sun. It is mesh material with double layers on the elbows and shoulder I think.
Very cool but it doesn't have any padding at all. I wear it so I don't feel guilty about not wearing any protective gear, it will probably save me from some road rash but I would still be hurtin' if I fell without padding.
Velcro on the cuffs so the sleeves don't blow up your arm at speed. Good quality and probably meant to be used under a light jacket in place of regular armor.
Since I try to ride in the mornings when it is cooler I usually wear a mesh jacket instead.