1/ Universal Sports Arm Band for Phones with their cases: Fits 3.5'' to 5.1'' cell phones (such as iPhone 4s, 5/5s/SE, iPhone 6/6s/7/8), with all cases such as OtterBox Defernder cases. Also fits iPhone X with Otterbox Commuter cases, and Samsung Galaxy S8, S7, S6, A5, A3 with slim cases on. See Product Description below for more compatible smartphones and cases. 2/ Premium Quality Materials and Universal Arm sizes: Made of Ultra lightweight, stretchable, soft skin-friendly, breathable Lycra and neoprene. Also, hand washable, water resistant, sweat proof and eco-friendly. Grip with compatible keeps the band firmly on your arm during at gym, workouts and running. So you can focus 100% on your performance comfortable. In addition, two dual-slot adjustable Velcro will fit arm size from 9'' to 16''. 3/ Reflective stripe for safe running in low light conditions. Built-in reflective stipe around the transparent window, provides the visibility in low light condition and keep you safer when running or walking at night or in the early morning.