TIRED OF RIDING LOW-QUALITY RENTAL BIKES WHEN TRAVELING IN EXOTIC LANDS?Montague, Inc. has the answer: folding mountain bikes. They make four models: Backcountry ($499), Crosstown ($599), Urban ($899) and the tandem TriFrame ($2495). All models, which fold to approximately 3' square, are guaranteed to assemble and disassemble within thirty seconds without tools, and can be checked as baggage when stowed in the optional Airline I or Airline II flight bags. Many airlines accept the Airliner bags as normal luggage, which means you don't have to pay the extra bike fee typically charged for a conventional bicycle in a box. For information and brochures call 800/736-5348 or 617/491-7200; on the web: