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Heat-Treated Alloy Tool Steel
The FR-4 is designed to fit the 20-spline tool fittings found on older SunTour® freewheels. Constructed from heat treated alloy tool steel, the FR-4 features a 1" tool fitting for use with an adjustable wrench, socket, or bench vise.
FR-4 Features
- Fits 20-spline tool fittings with an approximate outer diameter of 21.6 mm
- Fits Atom®, Regina®, splined Zeus®, and some Schwinn®-approved freewheels
 
            
            
            
            
             
           
          ![Shimano BUILT-IN TYPE Di2 BATTERY [SD300 TYPE]](https://unitedbycycling.com/cdn/shop/files/shimanoBT-DN300-di2battery_220x220.jpg?v=1735645011) 
          ![Shimano BUILT-IN TYPE Di2 BATTERY [SD300 TYPE]](https://unitedbycycling.com/cdn/shop/files/shimanoBT-DN300-di2battery-electronicshifting_220x220.jpg?v=1735645030) 
           
           
           
          
         
           
           
           
           
           
           
           
           
               
               
               
               
               
             
             
             
            