Description Milton S-521 Bayonet Tire Inflator Gauge - Single Air Chuck Head Key Features 1/4" NPT. Air chuck threads: 7/16"-27 UNS. Pressure range of PSI (10-120) and kPa (80-840). Includes: Bayonet-style inflator gauge, Single head air chuck, and 12" Hose. Replacement hose whip: Milton #526. Replacement air chuck: Milton #P500-44. All Milton replacement hose whips have 1/4” NPT threads and are interchangeable with any Milton bayonet gauge.