this is a replacement for the original x4 frame. it uses the standard 7mm motors (attention: 8.4mm motors on the h107c). the receiver can be screwed into the frame. I'd recommend to use electrical tape or a rubber band to attach the battery. the distance between two motors is 57mm instead of 65mm on the original body, which should result in more agile handling. update: first flight test was great, different versions are in the making (for the 107c motors, a bigger one for a more stable flight and a camera solution) UPDATE: A23 Version for 8.5mm Motors (Hubsan H107c) online UPDATE 2: As pointed out, the diagonal is 80.6mm 87mm version: http://www.thingiverse.com/thing:532432I recommend printing it in ABS.