These quality nozzles are used for propagation and watering of crops. They give very uniform coverage at the recommended spacing of 5'. They produce a fine mist that can be used with a propagation timer (short "on" time) for mist propagation benches, or with a standard irrigation timer for crop watering. Nozzles are shown in the picture in an ivy propagation/production range.
While these nozzles can be installed directly into threads cut into the (galvanized or PVC) pipe, the easiest way to install them is with the rubber insert designed specifically for installing the nozzles. A hole needs to be drilled in the pipe, push in the rubber insert, and screw in the nozzle and/or extension.
The pipe should be perfectly level to prevent dripping from the lowest nozzle(s) when the water is turned off. Using the anti drip riser with the nozzles helps greatly to prevent dripping if the pipe is slightly out of level, as is common in real life. Shown in the photo are the three separate parts, the anti-drip extension, the nozzles, and the two combined.