This listing is for a 4 pack of stainless steel automatic pig nipple drinkers. ½» bite size with wrench body for easy wrench installation. The stainless steel spring and dome provide long lasting protection from wear. Each nipple has a built in rear water filter mesh screen. Attaches to standard 1/2 Inch NPT Pipe Threads. This nipple drinker is ideal for sows and finishers. The drinkers are of stainless steel, solid one piece construction.