1.Easy to use, insert plug in the drain hole and tighten the handle until a slight resistance is felt, the rubber plug will be place.
2.Sealing the scupper holes for spilled oil or polluted liquids.
3.Specify the applicable drain pipe diameter when ordering, referring to the plug application list.
4.Rubber parts are made of oil resistant rubber(CR).

A scupper is an opening in the side walls of an open-air structure, for purposes of draining water. They are usually placed at or near ground level, and allow rain or liquids to flow off the side of the open-air structure, instead of pooling within the walls.[1]

Ship's bulwark and scupper in Russian and English
There are two main kinds of scupper:

Ships have scuppers at deck level, to allow for ocean or rainwater drain off.
Buildings with railed rooftops can construct scuppers to let rainwater drain off, instead of pooling within the railing of the roof. Scuppers can also be placed in a parapet, for the same purpose.

Traditionally, plumbers also use this as a water plug.