YONGNUO E-TTL YNE3-RX Wireless Remote Flash Receiver for YN-E3-RT/YN600EX-RT/ST-E3-RT/600EX-RT Wireless flash receiver, works within area of 100 square meters( without interference). Supports remote shutter release function and test flash. Supports flash mode: ETT, M, MULTI. Supports single contact flash triggering. Has PC output interface and allow to upgrade item online.