Print the wheels 3 times, one at a time and pause the print at 8mm, so you can insert the 608zz bearing before finishing the print.The top part needs to be tidied properly (or printed upside down) to be able to use the original screws.To install the part, the feeder must be detached from the UM2, by removing the cover over the steppers and all screws holding the feeder. Don't forget to hold the stepper when removing the screws.