The is one of the following closely-related slotted block belay devices:

Image Device
Advanced Base Camp (ABC) Catch Advanced Base Camp (ABC) Catch
Image Device
Faders Variable BelayC Faders Variable Belay
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Fixe Fixe

Each of these works much like any other slotted belay device. The control is good, but not as smooth as some of the belay tubes. Like the Wild Country Variable Controller, the two ends are asymmetrical, so these can be reversed for a slight change in feel. The asymmetry is less than on the Variable Controller, and I don't find the difference between the two orientations to be very great.

The cable keeper is stiff enough to not get caught by the rope.