Auto waterer nipple drinker. These are sold in single quantities (one per item ordered)
Use a drill bit size 11/32" at low RPM for PVC pipe or plastic 3-6 gallon bucket with somewhat thick plastic wall. For other thinner plastic walled items like water or pop bottles, use a 5/16" drill bit. Install nipples hanging straight down only. Use a little silicon or thread tape on the threads and screw the nipple into the drilled hole. Manufacturer recommends 1 nipple for 2-3 birds. These are for low pressure systems only (5.5 psi or less). Do not use directly hooked to a garden hose at normal hosehold pressures, you must use a pressure regulator if doing so, and reduce the pressure down to 5.5 psi or less.