Slottolution Hybrid Wheel. Inner diameter 14mm, outer diameter 16mm. Fits to 14x1mm (5mm long) aluminium tube. As tire you can use o-rings 13x3mm, 13x2,5mm or 13x2mm...depending on the outer diameter of the wheel. Wheel inserts with a outer diameter <12mm fits to this Hybrid Wheel. Fits to 3mm axis.