Sta-Rite introduced their modular DE filters a few years ago. They use a single cartridge-style DE module. I have installed several of the Sta-Rite filters and everyone loves them. Pentair bought Sta-Rite and adapted this type of filtration to their existing tanks. A good idea that works well in a larger version. When used with a cellulose DE alternative (Purifiber, CF-138) you should have sparkling water with very little filter maintenance.