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:532432
I recommend printing it in ABS.