Elkhart 2-1/2" NST Elk-O-Lite Master Stream Nozzle.

Features
Durable, lightweight Elk-O-Lite construction
Constant flow/select gallonage: 300, 550, and 750 GPM settings
Excellent straight stream quality
Pattern easily changed under flowing conditions
Excellent for AFFF application
Gallonage easily changed under flowing conditions (even down to shutoff position)
Ideal for use on portable monitors, deck guns, elevated platforms, etc.
2.5" swivel base
Finish hard anodized with chrome plated trim