Studiohut 4 channel Wireless Radio Hot Shoe Flash Trigger Kit for Canon EOS, Nikon, Olympus & Pentax Flashes with 2 Receivers 4 channels ; Standard 1/4" screw mount. Low power consumption & maintenance cost; longer battery life. LED indicators on both receiver and transmitter. Test button on top of the transmitter Additional receivers can be purchased and used in multi-flash set-ups; Kit includes 2 receivers Maximum effective distance range of approximately 30m