Attachment allows you to replace the topeak front bag with 2 or more bicycles. Mountable diameter: Φ1.0 inches (25.4 mm), Φ1.2 inches (31.8 mm). Product color and size may differ from the actual product depending on your display type. Product specifications, logo design, etc. may be subject to change for product improvement. We also cannot answer measurements or personal fit that the manufacturer does not announce. Please be aware of