The cuff is neoprene. It is quite strong compared to other products "right markets" as I have ever had. Housing for galaxy S2 is a bit cramped, but putting a little talcum powder on the inside (with fingers extended, do not sprinkle because it is not advisable for the phone) it is easier to place slides or remove the cuff. The fastening strap that bypasses the arm seems a bit too long and so if you have thin arm at the biceps, it may not hold. In this case, you must paste additional Velcro to have a larger mounting surface. The seal is good in the rain, the water does not penetrate the pocket. For now, this is the best I've had the cuff. The other, less expensive, were of poor quality.