Dry airlock with marble for variable capacity tanks. Features a threaded shaft, and a plastic backnut with gasket that screws onto the underside.
The outside dimension of the threads is 1-13/16 inch, it will fit a hole from 1-13/16 in to 2-1/4 in wide. The inside measurement of the airlock is 1-1/2 inch.
Includes a marble with allows the release of gasses, but will not allow air into the tank. The marble is the sealing device, no water or other valves are used. Features a tab with hole on the top so you can attach a rope for raising or lowering the VC lid.