Adapter, 4 inch long with 1 inch x 14 female threads one end, other end accepts 1 inch diameter stanchion, no side hole. 

Morad Adapters:

• Made entirely in the USA.
• Precision machined and finished by hand with modern tooling.
• Dependable and rugged.
• Our products are trusted on military, law enforcement, commercial and leisure vessels around the world.