Made of high quality metal Easy to install and durable Extend or contract wheels. Distance Available in 6, 9, 12, 15, 18,22mm heights. These are only applicable to 6 hole style wheel hexagons such as 1.9 2.2" VP rims. Screws not included 6mm height does not fit TRX4 Specifications: Material: Aluminum Alloy Quantity: 4pcs Color: Black/Silver Thread Diameter: 3mm Wheel Hex: 0.5 inches (12 mm) Height: 6mm/9mm/12mm/15mm/18mm/22mm Center Hole Diameter: 6.7mm Package Content: 5 sets m hex wheels 4 pcs Note: Please allow slight measurement error due to manual measurement.