A tube within a tube can be screwed together to accommodate any transom thickness from 2-1/2" to 3-1/4". Carefully trimming the length of either or both tubes (while being careful to not damage the threads) will allow you to accommodate a transom as thin as 1-1/4". A threaded plug is provided that can be screwed into the end of the larger tube.
This drain assembly can be used to replace the original through the transom brass tube on the early Catalina 27. These early boats used the drain tube to drain any water that splashed into the lazarette from around the outboard. Inboard equipped boats still had the drain tube installed to drain the locker. The plug might be particularly useful if you have allot of people in the cockpit having hors d'oeuvres. Water will be coming into the locker instead of draining out! It is likely the hole formerly occupied by the brass tube will have to be enlarged slightly in order to accommodate the diameter of this replacement part.
Some owners of the first generation Catalina 22 have achieved some limited success using these fittings to install through the transom scuppers in place of the larger 1-9/16" ID brass tubes installed using our transom scupper installation kit. Since they are a much smaller diameter, they tend to be plugged by debris (leaves etc.) when installed in the open cockpit.