The Canon Speedlite Transmitter ST-E3-RT (Ver.3, 6651C001) is a camera-mounted radio flash commander for photographers who light portraits, products and events with off-camera Speedlites. It controls up to 15 radio-capable Speedlites, such as the 600EX II-RT, 430EX III-RT and EL-series flashes, and adjusts their settings remotely from up to about 30 metres away, even when there is no line of sight. A large backlit LCD makes groups, ratios and power levels easy to read and set in dim venues. The transmitter is sealed against dust and moisture to a similar level as Canon's professional EOS cameras, so it can be used outdoors with confidence. Version 3 is the current release of the transmitter and supports Canon's latest EOS R mirrorless cameras as well as EOS DSLRs. After comparing online prices, www.marvel.co.za should be the cheapest on this product.