Compatible with 9mm, 12mm, 15mm (100mm/110mm), and 20mm front axles. Appropriate adapters are required for 15mm and 20mm axles and are sold separately. Brand: ROCKBROS Product: Car Roof Rack Material: Aluminum alloy Weight: 1-Bike: 2.1kg; Size: 16.9*5.12 in (Length*Height) 2-Bikes: 3.4kg; Size: 32.3*5.12 in (Length*Height) 3-Bikes: 4.5kg; Size: 36.2*5.12 in (Length*Height) Color: Red Package include: Aluminium Alloy Bike Rack, Rear Wheel Sucker, Fixed Velcro for Crank Note: Maintenance lube is not included in the package. Installation: Step 1: Clean the car roof and sucker to ensure no water, sand or dust Step 2: Install the sucker on the rooftop Step 3: Press the cylinder rod until the white line is no longer visible (usually 30-45 seconds) Step 4: Fix the fork with quick release on the front sucker Step 5: Confirm the rear wheel position Step 6: Fix the rear wheel and pedal