Rubber pool plugs are made with 316 marine grade stainless steel washers and through bolt, oversized nylon wing nut and quality rubber for years of winter use.
For 3/4" wall returns, usually on gunite pools, use a #4 rubber plug or a #5 rubber plug.
For a 1.5" threaded skimmer or return fitting, use a #9 pool plug or a #10 pool plug. You can also use the Hayward SP-1022C plug, shown above in white plastic. For non-threaded 1.5" pipes, you can use #8 pool plugs, or #9 pool plugs.
2" pipe sizes can use the #11 winter plug, or the #12 winter plug.
All of our winter pool plugs are made of quality materials to withstand very cold temperatures without shrinkage or slippage. Plug your pool lines after the water has been drained or blown out of the pipes, to prevent water from entering the empty pipes.
These rubber expansion plugs are used at the pool, not on the pool equipment. A set of winter plugs for a pool will include plugs for return line(s), skimmer(s) (and) a pool cleaner line, if applicable.