Product Overview: The WHOOP Accessory HydroKnit Band 4.0 Storm Grey is a comfortable, water-resistant band designed for WHOOP 4.0 wearables, ideal for both fitness and everyday wear. Key Features: ‣ Water-resistant for fitness and swimming. ‣ Breathable HydroKnit fabric for comfort. ‣ Stylish Storm Grey color. Technical Specifications: ‣ Material: HydroKnit fabric. ‣ Compatibility: WHOOP 4.0.