YONGNUO RF-603C-II-C3 Wireless Remote Flash Trigger Kit for Canon 1D 5D 7D 10D 20D 30D 40D 50D Adding the locking rings Max sync speed: 1/320 second 3.100m transmission distance with 16 channels Type: FSK 2.4GHz wireless remote control system Shutter release: half-press, full-press, takes 7 - 15 days to deliver