SMC 

SMC 50 ohm sub-miniature series are a widely used general purpose RF connector meeting IEC 60169-10.  Smaller than SMA they feature a screw coupling and are suitable for applications up to 4 GHz.  SMC have a gold plated centre and outer contact and are suited to applications in all industries.  In common with the similar snap coupling SMB series, the centre contacts of SMC are reversed when compared with the larger SMA, with the plug having the female contact.

For details; http://www.coax-connectors.com/products/connectors/smc.aspx