Jadnashua
Retired Defense Industry Engineer xxx
Not necessarily...the diameter and shape of the grate adapter part could easily be 4", but it would taper down to a standard 2" drain line when you take all of the parts(while they do make 3" and 4" shower drains, you probably don't have or need one).Thanks, hopefully Terry or someone else who removes these allot will chime in.
When I stopped by the Ferguson supply house they said that was probably the type of drain that I had by showing them the pictures. The shower kit I'm putting in has a 4" hole so I will need to put in a larger drain for sure.