The 57 from Narda Microwave is a Between Series RF Adapter with Frequency 0 to 18 GHz. More details for 57 can be seen below.
Low PIM 7/16 DIN Female to SMA Female Low Adapter read more
The AD-1418-301 from Vida RF is a QMA - male to SMA - female between series adapter. It operates from DC to 6 GHz and has a VSWR of 1.20:1. It has beryllium co... read more
Low PIM Adapter 7/16 Female to Mini DIN Male read more
You can now find similar products from multiple companies on everything RF.