Cervelo's S-Series cable guides are made from molded polymers, the BB cable guides direct and manage your shift cables to the correct alignment for your frame. The material is incredibly strong and resilient to wear, while limiting drag from friction. All you need to do is identify the model and year of your frame, and select the correct cable guide. Installation is simple when your cables have been removed. If you have been using your existing guide for many seasons, examine it for wear or damage during your regular cleaning and safety check, and replace it when necessary.