The reason I was wondering is because a supply house here has both listed as elongated seats but one is priced $14 higher, the 154 is the higher one but no explanation for the diff!
The SS154 is their tradional stlyed elongated seat.
It has an "OG" detail around the edge of the lid.
I use them mainly on their traditional bowls,
Clayton, Carrollton, Dartmouth, Promenade,