This is a 5 pin Relay Connector (base) designed to work with either high capacity or standard type 12V relays, including the Tyco (Bosch) relays sold here on our site.  This base has a built in mounting tab for easy mounting to your panel, chassis, or other location.  In addition, these bases feature a "tongue and groove" type interlocking feature that allows them to be firmly connector side by side with one another.  This relay base is available with 16-14ga terminals or 12-10ga terminals.  Components are also available individually so you can mix and match to suit your needs.