The RootX 40 lb. box is used mainly by municipal sewer agencies and contractors who are treating larger diameter and longer lengths of pipe than residential service laterals. There are two 20 lb. bags of RootX in each 40 lb. box. When you are using the RootX applicator (FDU) you would use 1 -20 lb. bag to treat 400 ft. of 8 -24" pipe. If you apply RootX directly from the package without using the applicator (FDU), you will need 2 - 20 lb. bags or 40 lbs. to treat 300 ft. of 8 - 10" pipe.