MPOW Running Sport Sweatproof Armband Case + Key Holder for 5.5-Inch iPhone 6 Plus Not every armband is sweat proof, Mpow armband contains special sweat proof material, and we also add a sticky back tape to make sure the armband closed. Strong sticky back tape: We use the strong sticky back tape to make sure the armband do not fall off when you are exercising. The strong sticky back tape supports more than one million times use. Adjustable: Built in two regulating slots to make the armband adjustable and suitable for most people. Option A: 12.0-14.0" [30.4-35.5 cm] or Option B: 8.0-11.5" [20.3-29.2 cm]. The crystal clear protective film is soft, sensitive, so you can touch and control your cell phone when you take exercises, and it can also keep your screen away from scratches. The crystal clear protective film is soft, sensitive, so you can touch and control your cell phone when you take exercises, and it can also keep your screen away from scratches.