Freewheels are no longer developed beyond 7 speeds because they are superseded by Freehub Cassettes, but they are still available cheaply. You can have teeth from 13T to 34T which are what you want from gears. The number of gears only determine the smoothness of shifting, not the range of terrain it can handle. https://www.sheldonbrown.com/harris/freewheels.html Accessories Bicycles Parts Specials Tools View Cart Traditional Thread-On Freewheels This page lists traditional thread-on freewheels only, as used on older bicycles. Most newer bikes use Cassette Freehubs, see our Cassette page. Not sure whether your bike uses a freewheel or cassette? Click here! Compatibility Notes . 1-speed 5-speed 6-speed 7-speed 5-Speed Freewheels For frames with 120 mm spacing . Sunrace Sunrace freewheels are very reliable. 14 - 16 - 20 - 24 - 28t FW537 6-Speed Freewheels For frames with 126 mm spacing . Compatibility note! If your bike currently uses a 6-speed freewheel, it may