Keep your sit-on kayak in top operating condition with these Replacement Sit-On Kayak Scupper Plugs. Made to fit 11/16 to 15/16 scupper holes, these plugs seal the self-bailing scupper holes to keep extra water out of the cockpit of your sit-on kayak. Plugs help you stay dry and warm. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Kayak Accessories.