These are test parts to keep my femur servos cooler. They were designed for the PhantomX AX Hexapod but will attach to any AX servo you might need to keep cooler. Using 30mm fans and the 30mm grill (provided) and plan to do more testing but I promise they make a considerable difference. Use 2.5mm screws. Each fan, grill, screw set is about 15 grams. The fans I used are 12V and connected to the tibia servos. I used these parts from mouser.com: Connectors part # 538-50-37-5033 Pins part # 538-08-70-1040 Video demonstrating volume of 6 high speed fans: https://www.youtube.com/watch?v=n7wlunQmpUM Oh and.. my Sketchup source files are included to make changes easier.