Does any one know if there is a difference between Spectrapure and Filmtec membranes as far as how well they work. They both say that they take out 98% contaminates. Does one last longer? The Spectrapure is $79 for 60 g.p.d. vs. $45 for the same g.p.d. Filmtec. I see people talking about The Filter Guys, their other filters for the unit are also cheaper. Is that a good place to buy from. I am basically wanting to save money and not sacrifice quality, if someone could please tell me the differnce between Spectrapure and other brands. Thank you very much.