6 inch Barrel Extended for 12 ga shotgun

The start of the threaded portion of the 12 gauge Mobilchoke tube is located a nominal 41.5 mm (1.63 inch) from the breech end of the choke tube.

The length of the threaded portion is a nominal 9.15 mm (.360 inch).

The major diameter of the choke tube thread is 20.62 mm (.811 inch).