Poly-choke Adjustable Choke outer collar ONLY 16 gauge OLD EARLY TYPE 16 TPI non-vented. Note that the outer collar is only half of a complete choke. This older style type example is an obsolete type early version that has 16 threads per inch instead of the newer standard of 24 threads. Some storage deterioration should be expected from items of this era, see pics of lack of heavy damage or major blue loss. There is also the vented compensator type available, as seen in other items here, and complete poly-chokes are available and ma y be installed here, too.Older thread pitches have been from 16 per inch up to the newer type standard of 24. Thread pitch of all newest series is 24 per inch, with outer thread diameter (of the threaded collet on the barrel) as about. Numbers are approximate but will work to verify fit of collar. Any questions, please provide details in message. Trained gunsmith, 30 years experience. Some parts may require professional fitting, installation, or exam by an experienced repairman to determine suitability. This item is in the category "Sporting Goods\Hunting\Gun Parts\Shotgun Parts". The seller is "k3480" and is located in this country: US. This item can be shipped to United States.