Secures to a pre-installed cargo/luggage/carrier rack with a dual-spring suspension adapter, fitting racks 120-180 mm wide with a minimum 55-pound capacity. Its innovative twist-closure design allows for tool-free installation and dismounting to transfer between bikes (with rack). Anti-theft lock and keys included. This style accommodates e-bikes, carbon or non-standard frames with an installed cargo/luggage/carrier rack. Fits Hamax Caress model rear child bike seats.