Just wanted to chime in here as I have used these armwarmers for several years, just so people have some comparision.

http://www.teamestrogen.com/prodDF_SSKW.html

These are made from a medium weight knit in white, so they are not light. I ordered the small/medium and even though I have small wrists I find it a bit tight on the cuffs. The top is a roll top and is very comfortable.

I wouldn't say there's a cooling effect at all but your arms are OK warm and it does help keep the sun off (I haven't been burnt through them). As it is a knit you may have to put sunscreen underneath just to make sure. They roll up as per standard armwarmers.

They work but of course I wonder if the arm coolers would be better being a lighter fabric???