This design uses one 10mm bicycle axle (cut in half), a few 10mm nuts and various sized sealed bearings. SUPER SMOOTH! Gap is approx 7.5mm (use the "rotated" version for best print with little to no support needed.)you will need to aquire: two 10mm bolts(or one axle cut in half) 4 10mm nuts 4 26x10x5 sealed bearings 2 19x10x5 sealed bearings Bearing sizes dont matter too much,but dont exceed 26mm on the stacked ones(one above the other). There is approx 27mm between the center of the two 10mm axle holes.