The first 3000 or so of the Kids 24" bikes used this unique derailleur hanger. Cannondale changed and standardized productionto use the KP284/ derailleur hanger. If your Trail 24" bike needs a derailleur hanger, measure the distance between the the hanger mounting holes. This KP316/ is 24mm. If it is larger then you will need the KP284 hanger.