Both devices are suitable for belaying a lead climber, bringing up two seconds or abseiling, with high levels of braking performance to assist the belayer in the event of a leader fall. The unit can be released using a karabiner, when bringing up a partner, by using the small eyelet and rope can be paid out faster by holding the device in the 'open' position with the thumb or a karabiner.
As both the Mega Jul and Micro Jul operate differently from other belay devices on the market, Edelrid have produced a video, which demonstrates the operation of both devices in various modes. See below. There's also a UKC Video on the Micro Jul below.