1 Efficient Urban Bikes: Felt X-City 1 & Dahon Jack by Justin Thomas • March 12, 2010 Versatile urban travel: the Felt X-City 1 bike, and the folding Dahon Jack bike for under $600. Related Posts Efficient Floor Bikes + Spring: Efficient Ghostrider Bike + Xtracycle = Efficient Xtracycle: Efficient Bike Extender