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
- 1" hexagonal base can be used with 1" socket or wrench
  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
- 1" hexagonal base can be used with 1" socket or wrench
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