The holder consists of two parts, the base plate which holds the board and a top plate, which holds the fan. Both parts are connected with 4x M3 40mm screws, the baseplate mounts onto the printer with 4x M3 20mm screws. For the fan you'll need 4x M4 40mm. The short spacers go under the base plate, the long spacers go between base plate and fan holder. The base plate is designed to fit on an Orca v0.2 but it can easily be modified for other printers. A 80mm fan is used which can provide enough cooling even at low speeds (less noise). The design is open to allow good air flow. Known issues: When the fan is mounted, it is not possible to reach the terminal screws for the thermocouple connector or connect the endstop cables.