This is the Yongnuo YNE3-RX receiver for Canon RT
Yongnuo has released photos of the YNE3-RX, their upcoming radio receiver that will let you add any flash to a Canon radio system.
Tag: YNE3-RX
Yongnuo YNE3-RX receiver announced; adds Canon RT functions to any flash
Yongnuo has announced an upcoming product called the YNE3-RX, expected to be a universal receiver for the Canon RT system.