Your Temper Assist Valve (TAV) cap has a rubber gasket which seals the valve when the cap is closed. Occasionally, changes in temperature and humidity can cause the gasket to shrink or expand and fall out of the cap when it is removed. We include a spare gasket in every repair kit for this situation.  This is an extra spare which has a PSA adhesive backing for a permanent replacement, so you only need one per cap. 

Note: For a permanent fix, remove the original gasket from your cap and replace with the adhesive backed replacement and keep the original in your repair kit for an extra spare if your paddling partners forget one.

Sold singularly; increase quantity for multiples.