Pixel Opas is compatible with Pixel KING"s system,It can work with KING"s transmitter as a manual receiver. This item only include one Opas, you should purchase at least 2 pcs to work together,the one works as Transmitter,the other one works as Receiver. Or you can use it with Pixel"s King(Tx). * Opas has a 3.5mm output socket. It can be use to connect your camera"s shutter remote port, or connect the studio flash via attached 3.5mm to 3.5mm sync cord, or connect with the flash via PC sync cord . * Opas is using global free channel 2.4GHz and FSK modulation system to make the performance more stable, and work in bigger distance(400m). Particular saving power design can make battery last more time. * Opas"s greatest feature is that you can remote control one cameras at the same time sync with multi flash, but do not support multi camera sync multi flash,e.g. two EOS 5D mark II with 4x 580ex,only one camera can sync the flash. * Compatible with Nikon: D7000, D5000, D5100, D3100, D3000, D3, D700, D2 series, D300 series, D200, D90, D80s D70 series, D60, D50, D40 series, F6. Nikon i-TTL COOLPIX: COOLPIX8800, COOLPIX8400, COOLPIX P5000, COOLPIX P5100,COOLPIX P6000. FUJI: S5 Pro. Compatible with other brands flash (Flash Wake up can only used in TTL Compatible flash).