The Sekonic L-858D is kitted wiht RT-GX Transmitter module. The RT-GX is a user-replaceable radio module that fits neatly next to the batteries in the SPEEDMASTER L-858D Light Meter.Less ThanBrGreater ThanThis kit brings a fully integrated light metering workflow to Godox users, making it possible for them to measure effortlessly, control, and analyze the characteristics of flash like never before. The Sekonic RT-GX simplifies the process of lighting a portrait, analyzing a scene and helping you quickly dial in your lighting recipe to get to your final image with exacting precision.Less ThanBrGreater ThanSekonic Speedmaster L-858D-U is the world's first multi-function, multi-brand wireless triggering light meter.