Our DVR3 and DVR4 regulators are designed to be attached to a flat metal surface via the supplied bonding pad to provide a path to conduct heat away from the electronics (ideally a flat bulkhead away from direct engine heat). If this is not feasible this strongly self adhesive heat-sink affixed to the regulator will limit its temperature rise when placed in a cooling air stream. The low heat output from versions up to 22 Amps * means that the extra heatsink is not of practical benefit. But regulators from 22 up to 40 Amps will run significantly cooler.
It is worth noting that the heatsink will give only a limited cooling effect if surrounded by the original control box casing, so that air movement is restricted. In reality the heatsink is actually a device to facilitate heat transfer. It does not somehow swallow up the heat from the regulator. It simply increases the surface area contacted by the air. If the air is not free to convect away the result is hotter air and a hot regulator casing.
The size of the heatsink is 40 x 40 x 18 mm.