Pack of 5
To be used with a water source of low pressure of 5 lbs. P.S.I. which is provided by a pressure reducing valve or by gravity tanks placed less than 5’ above the drinkers. You can use a pressure reducing valve or gravity flowing water. Very sanitary. They use a spring for shut-off which is very accurate. Water will only flow when the birds beak is in the cup. These cup systems avoid the messy wet spots you get when using nipple drinkers. 
About 1/8 of an inch of the threads will be showing once screwed into the pipe bracket or the cage/wall bracket. Over-tightening will cause the bracket to split