This is one of our most popular bearings assembled in an adapter that is designed specifically for a 3-1/2 OD x 7 ga. roller with relatively light loads. A metal shield ring supports a polymer sealing ring to hold out small amounts of large particle debris. A hole through the inner race allows the bearing to be regreased through the axle. Bearings that are regularly regreased can withstand very high levels of debris without damage. The bearing is lubricated with grease and can be used in powered applications as well as gravity applications. Grease allows the bearing to be used for powered applications but also recommended for gravity applications with 3.5 OD rollers.