I picked up this beautiful pen from Chatterley Luxuries.

Measurements
Length (capped): 173.6 mm/6.84″
Length (uncapped): 150.6 mm/5.93″
Length (posted): N/A
Diameter (section): 13.3 – 14.4 mm/0.52″ – 0.57″
Diameter (barrel): 17.2 – 18.1 mm/0.68″ – 0.71″
Weight (all): 45 g
Weight (cap): 29 g
Weight (body): 16 g

A superb artist’s rendition of a one-way shutoff valve.