The Co-Pilot Expansion Module allows you to increase the capacity of your existing Pilot™ HM2 from two bikes to four bikes. This modular design with optional expansion capability makes the Pilot™ HM2 and Co-Pilot™ combo a great choice. For cross-town transport to the trails or loaded up for a road trip, the Co-Pilot™ provides safe and confident transportation. Constructed of powder coated steel. The padded ratchet arms hold the bikes securely by the front wheel. Ideal for carbon framed, full suspension, and fat tire bikes. Lifetime Limited Warranty. Some assembly required.