The Velcro Strap ships with every order, but you can purchase replacements here. Use the Velcro Strap to connect the RepOne Sensor tether to anything you're tracking. The inside surface of the Velcro Strap was designed not to stick. If you're attaching the tether to a barbell, make sure to attach it loosely so it can slide as the collar spins, preventing the tether from wrapping around the bar and reducing measurement accuracy.