This double rope belay device can be used as a standard belay device with single or double ropes but also works in guide mode where two seconds can be brought up and either will be automatically locked off if the belayer's hand lets go of the rope. In addition it has assisted locking for working sport routes and use at the climbing wall etc.
The small eyelet is for releasing the unit with a karabiner nose when bringing up your partner (some people tie a small loop of cord through it). The assisted locking, as with all similar devices, can jam up if you haven't figured out how to work it (RTFM!!), but one mastered is simple to use and it will be found that the rope can be paid out fast and smoothly to a leader by holding device in the open position with the thumb. The body of the device is made from durable stainless steel.
Suitable for 7mm - 9mm double and twin ropes and 8.9mm to 10.5mm single ropes.
It is well worth watching the video to get some idea of the full range of use that the Mega Jul offers.
Weight 69g!
Also check out the Edelrid Micro Jul - a smaller version suitable for 6.9mm - 8.5mm twin and double ropes and 8mm - 9mm single ropes.