Design idea Stretchy loop nylon strap enhances nylon bands in take-on, lightweight-structure, works for Vivofit 4. New Case Performance Unique stretchy loop design with distinctive elastic strap creates an elegant look, and keeps your watch snugly to your wrist or arm for improved workout experience. Quality materials Made of premium nylon, breathable and washable. Soft and comfortable feeling provides good time all day. ANTI-ALLERGY DESIGN Held up extremely well with no signs of wear, not itchy as the original silicone band irritates the skin