A chrome plated brass shank 140mm long for your beer tap, with a barbed 6.35mm outlet.

Length: approx. 140mm (2-3/4")
From: Krome Dispense

A shank is used to attach a beer tap to a housing (i.e. a fridge door) and to the beer line.
The length of the beer shank determines how thick the wall/door can be you can attach the beer tap to.