The Hydroknit Band Is Our Fastest-Drying, Most Advanced Fabrication Yet. It Dries Twice As Fast As Superknit And Retains 30% Less Water – Making It A Must-Have For Water Sports, High-Sweat Activities, Or Just Taking A Shower. Includes Band, Hook, Clasp, And Fast Link™ Slider That Makes Swapping Bands Easier Than Ever. Only Compatible With Whoop® 4.0.