This is the 5.0mm Security Bullet Connector from Ultimate Racing. It features a 3mm set screw that when screwed in, expands the tip of the male connector so that it presses against the female connectors of the battery, improving the connection and securing it without the danger of unintentionally disconnecting.

It has a hole on the side to solder the wire. 12AWG wire is recommended.

The upper surface of the connector is grooved to provide you with something to grab on to easily plug and unplug the battery leads. 

It is bronze colored and has ULTIMATE RACING ORIGINALS laser engraved.

The package includes two connectors and two set screws.