PocketWizard Plus X Radio Trigger with 10 Channels (Set of 2) with Carrying Bag for 2 Triggers and Accessory Kit LONG WORKING RANGE: 344 MHz frequency working range of up to 1600 feet 10 CHANNELS: 10 standard channels let you choose your own zone BROAD COMPATIBILITY: Works with all PocketWizard transmitters and receivers including PocketWizard-enabled photo gear INTERNAL ANTENNA: internal antenna minimizes visual obstruction between you and your subject AUTO-SENSING: Intelligently switches between transmitter and receiver modes as needed