This is the replacement Magnetic Connector Ring for the UNI Cartridge Battery.  They are sold individually.

The Yocan UNI Magnetic Ring is designed to be easy to use. Simply connect your favorite cartridge to the Yocan UNI Magnetic Ring, slide it into the Yocan UNI, and wait for the magnetic connections to snap into place. The Yocan UNI Magnetic Ring was designed specifically for the UNI Box Mod. This magnetic ring enables the Yocan UNI to accept the vast majority of 510-threaded cartridges on the market today.

In The Box
1 Yocan UNI Magnetic Connector Ring