I acquired my Matrix from Mountain Gear in 2004.
The Matrix is a 2-slot hybrid belay device forged from aluminum and soft anodized. Mine is 77 mm. long, 43 mm. wide, 95 mm. high, and weighs 65 g. The rope holes are 40.5 mm. long and 13.1 mm wide. A release tab at the side has a 13.3 mm. by 18.4 mm. carabiner hole. The top surface is flat except for a raised area on the rib between the two slots, and rounded rope grooves that extend down the end opposite the tab. The bottom surface is irregular. The Matrix comes with a plastic covered cable keeper.
The Matrix has a rigging diagram stenciled on one side and the mammut logo stenciled on the other.
The Matrix is another solid belay device. It has some more effective mass than some of the tube belayers, but it can still get hot. The slots are a bit long for my taste, and do not produce as much friction as shorter slots would.
The bottom surface of the Matrix is convex where it touches the carabiner, much like the Trango B52. I find that this tends to push the carabiner to one end or the other - but which end varies with conditions. In either case, this probably increases friction somewhat, but I really don't notice a strong effect. Curiously, the bottom surface is almost a mirror image of the one on the Metolius BRD. Both devices work well so I don't see that the bottom surface shape is all that important.
The tab functions like the tab on the Metolius BRD, aiding in lowering. Like the Mammut Matrix, the tab has a carabiner hole. Not only does this lighten the device, it also provides a secure place for attaching the Matrix to my harness when I'm not using it. It also provides a place to clip the anchor carabiner when used as an autoblock (see the Trango B52 page for an illustration)
DO NOT hang the Matrix by the keeper cable when using it as an autoblock. The cable is not strong enough to support humans.
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