Dog Rocks are made from naturally occuring paramagnetic igneous rock. All natural minerals, no chemicals straight from the earth. Dog Rocks are a new product mined in Australia that helps to prevent those nasty yellow burn patches from appearing on your lawn. Dog rocks have been laboratory tested and are safe for your pets. Dog Rocks filter out impurities from water such as tin, ammonia and nitrates. These impurities are usually passed out through urine and when your grass comes into contact with these elements, it is burned, resulting in dead and yellow patches on your lawn. Without the impurities in the water, Dog Rocks actually help your dog fertilize your lawn. This is great for you, your dog and your lawn! 1 Bulk pack of Dog Rocks is approximately a 6 months supply.