Giant Gear Hanger Derailleur hangers or dropouts are a breakable bridge between the bicycle frame and gear derailleur, protecting the frame from damage if gear components are impacted. Dropouts should be inspected before every ride and replaced immediately if damaged or bent to prevent potential failure and subsequent frame damage. Dropout hangers are specific to the bike and model year, if you are unsure of which replacement hanger you require please email us with a picture of the old hanger along with the year and model of the bike.