i have trs drives on my fountain can i use #3 lower units on my trs top half of the drives . thanks for the help...

No. 3's are totally different. Someone else may chime in but I think SSM#2's match.

The SSM#II uses the TRS upper.

Yes In The Pink is correct. The SSM #2 look cool but are susposed to be weaker than TRS lowers, and the SSM #2 lower is lower in the water. Stick with your TRS lowers. Cheaper to rebuild than SSM#2, unless you have already blow a drive then consider switching to Konrads. Everybody that has them swear by them. THEY ARE BULLET PROOF.

thanks guys for all your help....