Great product! I have 11.5″ bicep and medium fits great. Used them during a 740 mile gravel bike race across South Dakota in the middle of July and they performed amazingly well in the heat and sun. They even saved my forearm from serious injury when I wiped out going too fast around a paved downhill corner. The sleeve took the brunt of the fall ripping in several areas.
I only lost a couple layers of skin and was able to stay in the race. I got them because I was looking for a sleeve with a thumb hole, wanted white with no logos/artwork printed on the sleeve. The unique cocona polyester really intrigued me and it works great for cooling. Made in USA a plus too!