The absolute best for protection from stings and cool is Golden Bee Products. They advertise in Bee Culture and ABJ. It is three layers of mesh and the bees cannot sting through it at all and the breeze blows right through. On a hot day I put it on with only a pair of shorts and boots under it. It's expensive and worth every penny.
If you just want cool and don't mind a few stings, the "Bug Baffler" works pretty well. www.bugbaffler.com
I have the jacket and pants which I, again, wear with just shorts and boots. But I also have the seperate standalone veil which fits easily in my pocket for those quick inspections. The bees can sting through the Baffler where it sticks to the sweat on your skin, but if your hives are calm it is just as cool as the Golden Bee Products but lighter and cheaper.