This replacement Palm webbing strap is a backrest part commonly used in whitewater kayak seat outfitting.

The Webbing (1 inch or 25mm) features a Plastic serrated strap sewn onto a length of webbing-  and is used in kayak seats to tighten the backrest (once you are seated) and secure you in position to give you maximum control. The Plastic strap has serrated ridges so it can be secured using a ratchet buckle (similar to snowboard bindings etc.) These ratchets are normally located on the inside of the cockpit rim.

This particular version of the strap is found on Dagger contour light backrests etc. but is compatible with many other brands including Wavesport.

If your ratchet are mounted on the backrest rather than the cockpit coaming you may find that this strap will still able to be utilised