What is the Difference between these cells, is it just because one is a dry cell and another is a wet cell? and what is the Mk1 and Mk2?? I've been reading all this stuff on here and need some straiting out!

I'm going to order some 316 SS plates from a guy on eBay that will cut them to size (even said he would make them 2"x3"). and i can get PVC shower pan liner that is 1.01600mm from the home depot! (it is Oatly shower pan liner 40mil) and that is pretty darn close to 1/32 in! (1/25in).. going to give it a go!