I have an older tub with a Brett Aqualine em-203 pack and the that looks like the EXHECB150 on spapartsnet. I need a new pressure switch as the existing one was leaking. When I went to remove it it virtually fell out. The pipe nipple part had corroded away. The switch is a tecmark model 3010. I did a parts search and found the 3010 and a 3010p. Whats the difference between the 3010 and the 3010p pressure switch? Is it just that one is stainless and the other one is plastic? What is the nut in the picture of the 3010p?

and after further review; how about the difference between thos listed above and the 3029 & 3029p?