Watco Push Pull Bathtub Stopper with s 3/8 in. and 5/16 in. combo Pin Adapter. This bathtub stopper is great for a repair, upgrade or to replace. Bathtub drain will need to have cross bars with either a 3/8 or 5/16 in. diameter for the pin adapter to thread into the drain. This Watco stopper is a great addition to existing bathtub accessories. Color: Chrome Plated.