Irudek D4 self-locking descent device for rescue of two persons, blue/black The D4 is a descender designed for the most stringent users. Due to the metallic manufacturing of all its components, this descender is resistant to wear and tear, bumping and corrosion, far superior than conventional devices. With this device, the user has precise and progressive control of all ascent handling and sloping plane progression, as well as the descent speed, even when wearing gloves. It also includes a double-lock anti-panic safety system. The permitted maximum load of 240 kg enables the simultaneous descent of two persons in case of rescue, and makes it one of the best options when it comes to tension release systems.