This is a drain plug that you remove to allow water to drain from inside the hull of your kayak (ski or boat to the outside). You may not need to do this but your craft will likely have a hole just in case. These suit holes without thread. This plug is not for scuppers (when removed these let water off the top of your deck or cockpit into the water- these are typically a lot larger. Suits particularly SSLSA or downwind Composite skis as well as some sailing dinghies Size Height Suits Holes with Diameter Range 4 13mm (7/16in) 12 – 15mm 5 25mm 13.2 – 16.1mm 6 15.9mm (5/8 inch) 15 – 18mm 7 26mm 16 – 19.3mm 8 32.5 mm 17.5 – 21.6mm 9 32.5 mm 18.6 – 22.7mm 10 20 – 25mm commonly cause the bung plug to pop out (or get jammed into position). Having a breather hole means you can leave the bung in the hole except when actively emptying your craft reducing the risk of losing it. Note this plug is not threaded it’s held in by friction (you jam it in) – some craft use threaded bungs (e.g. Bic skiff, Finn Kayaks, and most spirit kayaks etc.) These are also available. A rubber plug with a breather tube to allow for expansion and contraction due to temperature change is available here (one size also suits lasers).
