Seabung's revolutionary design allows the replacement of ball valves attached directly to thru-hull fittings secured by a lock nut while your boat is in the water. This allows you to perform emergency maintenance on water inlets and outlets in between scheduled haul-outs.
Should there be a catastropic thru-hull failure - due to structural failure from corrosion, or as the result of a collision - the Seabung can be used to quickly plug an intact (undamaged) thru-hull hole as a temporary emergency measure.
If one were at sea at the time, prudence dictates replacing the Seabung with a wooden plug, which will swell and lock in place, as soon as possible.
Seabung is made of a flexible, elastomeric polyurethane outer with a stiff, tough ABS core.
It is supplied as a pack of 2 sizes of bungs for thru-hulls holes sized 3/4" - 1-1/4" (19mm-32mm), and for larger thru-hulls from 1" - 2" (25mm-63mm).

* A few words of caution and common sense when using the Seabung.
If the seacock is secured to its backing plate with screws, it may be rotated off the thru-hull without breaking the bedding seal under the head of the thru-hull. However, if the seacock requires significant torque to be removed, before removing the seacock, it may be necessary to first secure the connected thru-hull from outside the hull to avoid damaging the bedding seal between the thru-hull and the hull.
If the seacock is secured to its backing plate by sliding onto bolts embedded in the backing plate, then the only way to remove it is to unscrew the thru-hull from outside the hull.
You should continue to carry wood plugs in your boat the Seabung is not meant to replace these important safety devices.