DETAILS: Trek 2012 FX and District bicycles imported by the Trek Bicycle Corp. of Waterloo, Wis., and sold at specialty bicycle retailers nationwide between May 2011 and September 2011 for between $550 and $1,100.
WHY: The bolt that secures the seat saddle clamp to the seat post can break, posing a fall hazard.
INCIDENTS: Four reports of incidents, with one injury involving a broken tooth and lip injury.
HOW MANY: About 27,000.
LIST OF MODELS: 7.2 FX WSD, 7.2 FX, 7.3 FX Disc WSD, 7.3 FX WSD, 7.3 FX Disc, 7.3 FX, 7.4 FX WSD, 7.4 FX, 7.5 FX Disc, 7.5 FX WSD, 7.5 FX, Livestrong FX, Livestrong FX WSD, 9th District, Livestrong District, and District.