Trigger Systems has been testing the PLATINUM series roller-fleece sumps for over a year and a half to make sure we have a solid, proven design. This series includes an automated, continuous mechanical filtration that replaces filter socks. We tested several different designs and found that having the fleece roll system sized to the sump is by far the most efficient. Trigger Systems fleece rolls have been lasting 4 to over 6 months, unlike filter socks that need to be changed every few days. Every user so far has reported improved water quality, with some stating algae is no longer a problem. The fleece rolls are 8″ or 10″ wide depending on the model and 150 feet long. Each sump comes with 2 rolls in the box.