PREMIUM FKM MATERIAL: AVEKI Fluorine Rubber watch band is made of flexible elastomer waterproof material. Sweat and water resistant, lightweight and easy to dry, great choice for swimming etc. Durable premium material can prevents skin from irritation. Very soft and comfortable to wear.LOCKING FEATURE: Each Fluorine Rubber watch band comes with a special rubber loop. It has a bulge inside, which can coincide with the large hole at the end of the strap, so this special loop can fix the strap and make it difficult to slide.SMART WATCH WIDTHS: 'Product Description' section on this page lists proper widths for Amazfit GTR 3 Provivoactive4/GarminActive and More.MUST READ BEFORE ORDER: In order to save your time and effort, please choose the correct size for your watch. Accuracy to the millimeter is very important. AVEKI provides 20mm , 22mm watch bands for you. Please feel free to contact AVEKI Service if you are not satisfied with the watch band you received. We will provide you a satisfied After-Sale Service.