This is an easier way to keep your yard free from dog waste. The Doggie Dooley installs into the groungd and then operates like a septic tank by using bacteria action to liquefy pet waste for ground comsumption. Digestive action works best at 40 degrees or above.Model 3500-has a pryramid shaped plastic tank with the capacity for 1 large or 2 small dogs.Model 3800-is the same as the 3500 with an added extension for up to 4 large dogs. Both come with a foot-operated lid, 8 oz. of digester and a free scoop.