This is a motor mount for Flite Tests F22 build. It is very rugged! The whole plane takes about $2 worth of Dollar Tree foam board. Motor slots are slightly dynamic so as to accommodate different size motors. The holes are about 3mm in diameter as designed. The plane in the picture used 2-56 nuts, bolts, and washers I believe. Attached are pictures of my friends plane with one mounted. http://flitetest.com/articles/ft-22-raptor-project 1) Print it. 2) Attach motor with propeller. 3) Align motor mount so that propeller is in the middle of the open slot (prop slot). 4) Hot glue in place.