Studiohut 16 channel Wireless Radio Slave Flash Remote Trigger complete with 4 Receivers Kit Low power consumption & maintenance cost; long battery life. LED indicators on both receiver and transmitter. Test button on transmitter for test firing. Additional receivers can be used in multi-flash set-ups to trigger all lights wirelessly. Typical battery life of about 20,000 usages. Maximum effective distance range of approximately 21 yards (20m)