Micro BNC 75 Ohm 

Our Micro BNC 75 ohm connectors are designed for HD & UHD Broadcast, Telecom, HDcctv, Instrumentation and similar applications that require high performance in an high density package.  The unique patented coupling nut allows the use of a special tool to disconnect the connectors when they are closely mounted. Tested to beyond 12GHz and exceeding the requirements of SMPTE ST 2082-1, these connectors are used in Full HD1080p (3G), HD-SDI and are fit for Ultra HD 4K (12G) applications.  With a diameter of only 7.8 mm, mounting density is increased by 4 times when compared with a standard BNC.

For details; http://www.coax-connectors.com/products/connectors/bnc-micro-(hd-bnc)75-ohm.aspx