From the folks at Slot Car Corner:
A new Super Tire, the 1422C, is now available. It fills the gap between the popular 1421C and 1423C. With an outer diameter of .758" (compared to .740" and .770" for the 1421C and 1423C respectively), it fits many popular F1 wheels (CB Design, Slot.It, etc.) and can also be used with CB Design 15x12mm wheels (o.d. is .809" when used with 15x12mm wheels). A "Yellow Dog" (urethane) version will be available shortly. For more information please go to the Slot Car Corner website.