3/4 inch outside bib-tap (bib-cock).
This heavy duty tap is made from brass and has an outlet hose union to take 3/4 inch hose.
Male thread is British standard pipe thread, 3/4 inch size.
Note : This is BIGGER than a regular outside tap - as the tap is larger than usual, hozelock style connectors won't fit on the outlet.
Pipe thread sizes do not match up with real life measurements. 3/4 inch thread size measures more like 1 inch with a ruler.
These are often used in an industrial environment, it's more normal to have a smaller 1/2 inch tap in a domestic setting.
BSP (British Standard Pipe Thread) sizes don’t match up with what you would measure using a ruler. Have a look at the BSPT link at the bottom of this page for more information about how plumbing threads are measured.