The is one of the following closely-related notched belay tubes:
Each of these is 53±2 mm. long and 46±2 mm. wide. Their weighs range from 64 to 95 g., with variations in the lightening holes (or their absence) accounting for the differences. Their slots are all 32±2 mm. long and 14±1 mm. wide. They all have plastic-covered cable keepers, with the Black Diamond keepers being and stiffer than others.
The Black Diamond ATC-XP was the first of these to appear, by many years. Version A was an improved version of their ATC. From there, the basic design evolved and similar devices appeared from others.
Each of these has V-slots to give additional friction for belaying
or rappelling. Each side of each groove has three V-shaped slots,
giving the grooves "teeth" to grip the rope more effectively.
These teeth act to guide the rope deeper into the slot, in much
the same manner as the teeth on the Wild
Country Hand ascender work. The teeth do not have the narrow
angle found on the Trango
Jaws or its equivalents, so they do not create the same wedging action. For this
reason, I find these less effective than the Jaws family. On the other hand,
the teeth on the ATC-XP provide a larger bearing area for the
rope, which helps reduce localized heating. These are more massive than the ATC,
but will still overheat on long rappels.
The ATC-XP and equivalents are rigged like the ATC, with the V-slots on the
brake hand end of the rope. Alternately, they may be reversed
to disable the V-slots.
Some of these have a hole or an opening in the sides and the central rib. When present, these reduce the device's weight, but also reduce the devices' surface area for rejecting heat.
My preference from this set is for the Black Diamond ATC-XP, Version C, which is the lightest of the group and has the stiffer keeper; however, it requires closer thermal monitoring on rappel.
