The recall involves certain models of Alpenchallenge, Urbanchallenge and Masschallenge bicycles equipped with full carbon Aprebic bike forks model ACC-A704DN50B. The fork model number is printed behind the top arch. Specific bicycle models included in the recall are Alpenchallenge AC01 105 Tiagra, Alpenchallenge AC01 Rival, Masschallenge MC01 Team and the Urbanchallenge UC01 Alfine 11. Both the Alpenchallenge and Urbanchallenge bicycles include the 2012 and 2013 model years. The Masschallenge bicycle includes model year 2012. The model year is printed on the top tube of the bike. The bicycles come in black and yellow, or black and red color combinations.