If PX is the Army term for Post Exchange, what service branch is BX used for?

A Base Exchange (BX) US Air Force terminology: also referred to as a Post Exchange (PX) Army posts, Navy Exchange (NEX) on Navy installations, Marine Corps Exchange (MCX) on Marine Corps installations and Coast Guard Exchange (CGX) on Coast Guard installations is a type of retail store operating on United States military installations worldwide. Originally akin to trading posts, they now resemble department stores or strip malls.

Over the next few years, every exchange operated by the Army and Air Force Exchange Service will be rebranded simply as an Exchange (X) to simplify differentiation between the similar sounding (BX) and (PX) names.

Exchanges on Army and Air Force installations are operated by the Army and Air Force Exchange Service (AAFES), while those on Navy bases are operated by the Navy Exchange Service Command (NEXCOM), and those on Marine Corps installations are part of Marine Corps Community Services (MCCS), which also runs the rest of Marine MWR operations. The Coast Guard Exchange (CGX) operates a handful of stores on Coast Guard installations. Exchanges on joint installations are generally served by the exchanges already operating upon the joining of the existing installations, though some smaller exchanges may close when they can no longer benefit the installation.