Summer weight arm warmers, sunsleeves or "coolers" in this case are exploding in popularity thanks to the sun protection, compression and cooling benefits they offer. The Craft Body Control Arm Coolers are designed to cover and protect the arms from the sun in warm weather. Thin, elastic knitted compression fabric has Craft's six channel technology to provide both muscle compression and cooling.
The tight compression fit reduces muscle vibration helping to keep the arms fresh during exercise. They could be even be considered a "secret" performance boost for hard mountain biking. The Body Control Arm Coolers deliver UPF 50+ sun protection eliminating sun damage and reducing the need for expensive and messy sun lotion.
Living down here in Alabama, I can't say they are cooler than going with bare arms during the summer. However, they are great for sun protection, and they are reasonably comfortable to wear in the heat if you are looking for sunprotection.
Pros: Light, breathable, good sunprotection
Cons: Not exactly arm coolers but still usable in the