The GMC Topkick 21-Speed Mountain Bike features a full-suspension, strong aluminum frame that utilizes a floating beam suspension design that is mated to a Zoom suspension fork with elastomer/spring technology. The Topkick's drivetrain starts with Microshift push shifters. These shifters control Shimano's tried and true TZ-30GS derailleur. The drivetrain finishes up with a strong aluminum wheelset featuring V-shape rim profile and high-flange alloy hubs. Stopping is handled by Promax disk brakes on the front and rear. These brakes are vastly superior to rim brakes, especially under adverse road conditions. True to it's GMC roots, this bicycle is rugged, good looking, and built for the long haul.