The holder is securely mounted on the top of the Z-axis with two screws, the roll and the filament guide are screwed as well; therefore troughs for hexagon nuts are providet inside of each. I use a unique bearing from an old harddisk for the roll, so for other bearings modifications are necessary. The holder is slightly tilted forward and the bearing mounted with the face upright to prevent the spool from touching it. The guide must be printed without support structure to keep the inside free.