F450 arm for M3 inserts without leg

UPDATED: See new design at http://www.thingiverse.com/thing:1206960

A remix of Spyda/F450 arms but without legs and ready to use M3 threaded inserts. They work really well printed with PLA at 30% infill, lightweight and doesn't flex :)

I use M3 inserts of about 4mm OD and 4mm height.