This is a center plate and other parts for a very common quadrocopter design using 10x10mm aluminum bars.
The centerparts are suited for electronics and frame parts from mikrokopter.de.
The design is quite rigid and might work very well without the center cross. Because the parts are printed with little infill the weight increase compared to the original center plates is quite low. In addition you get many advantages like antenna mounting hole, fitting bl-ctrl fixation, battery holder and so on.
More pictures are available on our blog:
Happy printing and flying!