The sleeve is tight yet cool and comfortable. The material is like under armor heat gear in terms of thickness and compression.
Just to give you an idea of its dimensions (as I personally always like to know when making purchases online), I bought the small size. It measures about 14 in long unstretched but stretches to about 15 or 16 inches to just above my bicep. The circumference is about 6 in at the wrist and 9 in at the top by the bicep. My arm circumference is about 6 in at the wrist and 12 in at the thickest part of the biceps unflexed. So the 9in at the top is a bit tight at the biceps but it does fit over the thickest part of my bicep and stretches enough to compensate. This size fits me well and stays in place even after prolonged periods.
Overall very satisfied and would purchase again.
Just remember that they come individually as mentioned in the product description so buy two if you want one for each arm.