The 4x9x4 Flanged Rubber (F684-2RS) Halo series of bearings are a high quality steel/chrome bearing with rubber seals. These bearings have been tested and proven by many racers.
Bearing Dimensions
METRIC: 4mm (Inner) x 9mm (Outer) x 4mm (Width)
STANDARD: 0.15748" (Inner) x 0.35433" (Outer) x 0.15748" (Width)