These filter balls only lasted a 1-1/2 years. When I tried to claim warranty on them, which is 2 years, it was rejected by the manufacture. Pool Supplies talked with the manufacture but got nowhere. This manufacture of the filter balls doesn't stand by their product at all. It was really easy to prove my old filter balls were defective, at start up this season pool was foggy and wouldn't clear after two weeks, changed the balls with new ones, pool went crystal clear within half of a day. Again it's a real shame to leave a bad review, as the filter balls do work, but I spent more on these filter balls because of the warranty. But that warranty means nothing as the manufacture doesn't stand by their product. I might as well bought cheap ones that are 1/4 of the price of these, and even if they just lasted one season, I would still be a better deal. I do recommend filter balls especially for people who don't want to waste a lot of water on backwashing, but I wouldn't pay the premium price from this manufacture for the warranty as they don't stand behind their product.