The Kupo thread adapter is a hollow 3/8″ screw. On the outside it has a male 3/8″ thread, on the inside you’ll find a female 1/4″ thread.
It works with the Kupo Double Head Stud w/ 1/4″ to 3/8″ thread, and make it work as a Double head stud w/ 3/8″ to 3/8″ thread.
Specifications:
Made to convert 3/8″-16 thread for 1/4″-20 screw. Comes in Set of 5