CMI has been producing figure 8 rings since 1974 and since then has sold about half a million of these descending and rappelling devices. Indeed, CMI earned renown mainly because of the figure 8s. These continue to sell today but there are now two versions –the CMI Standard 8 Ring, which is the older design, and the CMI Rescue 8.
Like its predecessor, the CMI Rescue 8 is constructed of hot-forged 6061 T-6 aluminum alloy. This is aircraft-quality aluminum that is hot forged making the device strong and less likely to fracture. This is because the molecular alignment of the metal is improved with hot forging. The Rescue 8 is also much lighter than steel and produces excellent friction. For protection from rust and for extra durability, it is anodized with a hard coating.
The upper ring of the Rescue 8 is larger than the Standard version. This is intended to accommodate heavy-duty large ropes, even two of them. It has horns on its upper section preventing the sliding up and locking off of the rope. The tie-in end has dual holes keeping the descender attached to the harness during the threading of the rope to the carabiner. This prevents dropping of the device in extreme situations.
Ropes sized at 16 mm double, and from 12.6 to 19 mm single can be used with the CMI Rescue 8. It weighs 221 g and has a breaking strength of 10,000 lbs.