I acquired this pair from Inner Mountain Outfitters in 1998. I acquired another in 2017 as part of Bob Thrun's collection.
The ascender shell is a roughly "D" shaped piece of painted 4.2 mm. thick aluminum bent to form a rope groove on one side and to hold the cam pivot and safety on the other. The handle opening is 106 mm. high and 55 mm. wide. There is a two-piece plastic hand grip bolted to the shell with three 4.6 mm. cap screws and hex nuts. The left rear and right front hand grips have round recesses for the cap screws, and hex nuts fit into hexagonal recesses molded into the left front and right rear hand pieces. Two 15.9 mm. holes at the base of the shell serves as a rope attachment points. A third 15.9 mm. hole provides a means to attach non-load-bearing slings to the shell above the cam.
The cam is a skeletonized steel casting. The conical teeth are oriented perpendicular to the cam face and are set in a (4.3)^3(4) pattern. The inner cam face radius reduces from top to bottom to accommodate various sized ropes. The cam and cam spring are mounted on a solid 6.3 mm. steel pin. An external retaining ring holds the pin in place. The cam safety is a plastic lever mounted on a 3 mm. semi-tubular rivet in the same shell channel as the cam. A second spring serves as a safety spring. Normally this spring holds the safety where it blocks the cam from opening. When the end of the safety lever is depressed, the opposite end pivots upwards so that the cam is no longer obstructed.
There are no markings on the ascender, but CMI applied two stickers. One reads "EXPEDITION ASCENDER," "Cmi," "Franklin, WV 26807," and "MBS: 3400lb (20.4 Kn)." The other merely reads "Tested."
Why would C.M.I., who makes the excellent UltrAscenders, introduce these beasts? For a very good reason. We don't run into it in caving or rock climbing, but in mountaineering one has to be able to work their ascenders with mittens on - and I mean big, clumsy, multi-layered mittens. For many years the Clog ascenders were the ascender of choice for this niche, but now C.M.I has produced some direct competition. I don't consider this ascender for caving, but for snow and ice, it has a lot going for it.
The C.M.I. expedition ascender has two tie-in holes at the bottom, while the Clog has none. The sling attachment holes could theoretically have the same safety problem described for the Clog ascender, so I don't recommend using carabiners in them. The handle on the CMI is bolted on, and is thicker, so for people with large hands, it is more comfortable. The safety arrangement is almost identical. One thing I like is that the cam is held in with a pin secured by a retaining clip instead of a rivet, so replacing a worn cam is easy.