Not any more. It was true until we developed our patented technology. Other manufacturers make the claim that they’re “closed” systems, but if you can see an opening in a curved system, then small debris can get through. Leaves, pine needles and oak tassels will sneak inside. This debris will remain hidden somewhere near or over your downspout and will cause a clog. MasterShield uses a filter to separate liquids from solids. As a result, MasterShield will never let anything but water into your gutter, one of the many reasons why we back it with our no clog warranty.