one size fits all WHOOP 3.0 & 4.0 Compatible Compression High Performance Track your data wherever your training takes you with our HydroSleeve, made to protect your WHOOP® 4.0 while in the water. It’s a 100% silicone, water-resistant, and elastane band that slips over your device and secures it to your wrist. Ideal for swimmers, triathletes, and other water sports or activities. Comes in packs of 2 and available in 3 sizes. Compatible with WHOOP® 3.0 & 4.0.