For quick prototyping on Raspberry PI when you don't want your infra-red LEDs connected directly to the night-vision camera. The voltage can then be supplied separatelly and controlled using GPIO and a back-current protected power source. Useful when the battery has to be preserved when the camera isn't taking any pictures.

The inside has a square hole where a heatsink can be placed. Don't let the 3.3V 300mA LED get hot enough to deform the plastic. Use infra-red protection goggles if looking into the light source or you'll end up with a very bad headache.

Legal note: LEGO lost a court case where it was decided that the standard itself cannot be copyrighted because it had mathematical features more suitable for a patent, which would've expired a long time ago if they would've filed for one. According to copyright law, it's okay to print parts compatible with LEGO, but not print a part of a standard design that would violate LEGO's copyright. The bottom of the mount does not immitate the design of LEGO in any other way than the dimensions needed for compatibility. Law is always fuzzy and changing, but this part is certainly both legal and ethical to print by promoting fair competition.