This listing is for 1 automatic cup style drinker with nut, o-ring, washer, & built in trigger. The purpose of the nut, o-ring, and washer is for connecting this cup to thinwall plastics. If the item your attaching the cup to is thin plastic and cannot make a few threads to attach cup, then this is the solution you need. This model is for mounting the drinker directly to you waterer, whether it be a bucket, pail, large pipe etc. Simply drill a 3/8″ hole into your bucket, thread on your drinker and install hardware on rear. Drinker cup is a breeze to clean as it is a quick disconnect orange cup. This unit will provide many seasons of trouble free use and can be used for many different birds. Cup utilizes a trigger system that automatically fills when the chicken pecks it. You can design your own drinker system and add as many cups to buckets or large pipes as you wish up to 210 drinkers per system. Drinkers work under low pressure at 5 psi or less. If you are wanting to hook your water system to garden hose pressure that is fine, but you will need a regulator in order for you to do so. .