Saris Bike BeamBy bridging the gap between the bike's stem and seat tube, the Bike Beam creates a virtual top tube that lets you bring any bike along for the ride The Bike Beam creates a top tube for mounting non traditional bike frames. Easy to use, the sliding collar feature ensures that your Bike Beam is securely installed on your bicycle. For use with racks where bikes are secured by the top tube, such as hanging style hitch racks, trunk racks or home bike