When the retainer is engaged the wedges expand, clamping the PCB to the cold wall. The thermal transfer depends on several factors. Generally speaking for Wedge Loks, the larger the profile, and the more segments, the greater the heat transfer. Specialty metals can be used for additional thermal performance. In order to yield optimal clamping force, thermal Wedge Loks must be installed properly, using a calibrated torque wrench, to the specified amount of torque for that particular model.