Stretchable rubber straps for bicycle racks - Qty: 8. The holes measure .486" and are typically used to fit over 1/2" tab. These can work with Thule and other cradles with protruding attachement knobs both on the sides of cradles.

Reference: https://www.amazon.com/Thule-534-Accessory-Strap-Kit/dp/B005AS3PXG