CRIC ACID FM ROOKIE M The extra-light ACID Kickstand FM ROOKIE fits all CUBE kids' bikes with the flat mount interface. Size M is perfect for bikes with wheel sizes 20'' and 24''. With a larger radius and soft edges, it takes its design cues from our CUBE kid bikes. The length is adjustable without the need for tools.fits all CUBE bikes with flat mount interface for wheel size 20'' and 24'' light weight tool-free length adjustment