These drywasher fans are designed for years of rugged service with sealed no-maintainance. bearings. The counter weights are adjustable. We have two sizes. A 4 inch fan unit for small to medium drywashers, like the smaller Gold Buddy or Keene 140 drywashers. A 5 inch unit is available for large drywashers like the large Gold Buddy and the Keene 151. A 6 inch unit is available for the Gold Buddy Stallion.