I like this design enough to give it three stars:
The following notched belay tubes, including the , are essentially the same device:
Each of these is 60±1 mm. long and 48±1 mm. wide, and has a weight in the 76±3 g. range. Their slots are all 33 mm. long and 15 mm. wide.
These are just like many other devices except for one little difference,
but that difference makes any of these a much better device than those others. The special feature is the teeth. First of all, if
you don't need them, turn the device 180 degrees and they are
out of the way. On the other hand, if you want more friction,
then these teeth canprovide it. This is the only device design of this size and
weight that I feel comfortable rappelling my 9 mm. haul line
on. With any others, I never really felt completely in control
(to be fair, I haven't tried this on the the Omega
Pacific SBG or the Simond Cubik).
The extra control is well worth carrying the extra 15 or 20 grams. One
caution: like all belay tubes and tubers, these can get very hot on rappels.
I borrowed the following paragraphs from Trango's web site, although they should apply to any of the devices in the table:
Jaws stops better than most belay/rappel devices. The addition of the V notches really grabs the rope, assisting in slowing down the fall. In lab tests using a UIAA drop tower, an 11 mm. rope, an 80-kg weight with a fall factor of 1.2, and a clutch holding the rope with a 50-lbf slip threshold, we found the following results:
Pyramid/ATC/Tuber style devices 16" - 20" slip, no rope damage GriGri 1" - 3" slip, no rope damage Jaws 6" - 8" slip, no rope damage Jaws allows you to adjust the rope friction during a rappel. By flipping the rope out of the notches and over the side plates at the start of a long rappel, you can reduce the friction the device gives you at the start. When the rappel begins to speed up as you get closer to the ground, flip the ropes back into the notches to slow it down.
You must rig Jaws correctly. It's not symmetrical so you need to be sure the notches are on the brake hand side of the rope, not on the side which goes to the leader. Also, because of the additional friction provided by the device you'll find that the beginnings of long rappels can be a bit jerky. The solution is to allow rope to slide through by varying the angle of your brake hand rather than just letting rope slip through. On low angle slab rappels, turn Jaws around so the notches are on the anchor side and your brake hand is on the smooth side.
