ISC D4 Descender

The ISC D4 is a double-stop work device with an auto-lock function (which is activated whenever the operator lets go of the handle) and a panic brake which is not overly sensitive in normal use.  The D4 cam is made from a super hard solid Stainless Steel and is highly wear and corrosion resistant. 

The D4 Descender features a unique and innovative progressive cam action, which offers control at slow or fast speeds. The progressive cam works by way of one cam operating inside another cam. It is also easy to back-feed the rope through the D4 and therefore it can be used for smooth ascending or for emergency hauling (when used as part of a 2 to 1 Z-Rig).

The D4 has a rated load of 240kg (529 lbs), making it a true Work and Rescue Descender. It is not necessary to build in additional friction to achieve these loads, although it can be useful to do so, for an even higher degree of control in belay applications.