DIG A201B Fertilizer - Filter Applicator Backflow Preventer Can hold up to four water-soluble fertilizer tablets inside the filter screen canister Includes a backflow preventer to keep contaminated water from entering the household water supply, providing protection from backflow and back siphoning of water All-purpose screen filters for use in drip irrigation or micro sprinkler systems Screens have excellent resistance to most common chemicals Large filter area and low friction loss allow for long intervals between cleaning while applying nourishment directly to the plant roots as needed