This crab shell is an excellent dry organic source of NPK, calcium (23 percent) and magnesium (1.33 percent). Crab shell is high in Chitin, which promotes the growth of chitin eating bacteria in the soil and when it is added to the soil it helps to create a hostile environment for the fungus and nematodes by feeding the biological life that eats chitin and chitin based organisms. This product weighs 4 pounds.