I designed this wheel because all wheels that I tried to print were too small and/or did not rotate well. You should print this part twice and glue the two parts together. The two-part design is in order to avoid support while printing. You should add an axis and a way to mount the wheel to the hamster cage. I used meccano parts for this (see photo). The final wheel is very sturdy and it rotates perfectly. My hamster is very happy :-)