Use the Assos Arm Protectors to protect from the sun. Through the years, prior to these or similar, the sun has damaged the skin on my arms significantly and I was ignorant regarding these products because I liked the look of the tan. These Assos products fit me the best as I have skinny arms and even though there is no silicone grabbers they slip down way less than the other brands. They definitely contour better and you can only laugh at the Left and Right markings on them. I have these in white and black.
I have purchased the Assos Arm Protector in white and black. During a minimum of 200 miles of riding in the Santa Monica Mountains, they provide full sun protection to my arms and kept my arms comfortable in temperatures between 60 and 90 F. I use the white arm protectors on hottter days as the black absorts more heat. Since I ride quickly, I generally have a cooling effect from the air passing by Assos has design these arm protector to shape comfortly to arms and be form fitting. These arm sleeves are pricey but I have found Assos quality stuff lasts a long time. They come in 3 sizes: 0, I, & II. Take your time to be sure the size fit your arms to achieve the proper size.
Bought them for riding in Phoenix heat. Perfect choice. Cooler than bare arms, no sunscreen needed. Fits snugly. Very comfortable.
I ride about 100 miles/week outdoors in hot/sunny conditions (mid-Atlantic coast) and these sleeves work very well. Lightweight, cool, comfortable, and great UV protection. What's not to like? So happy with my original purchase that I bought a second pair.