The GF Series freewheels are self centering. From size 8 to size 20, centering is steel on steel, while from size 25 to 130, centering is ensured by 2 160.. series bearings. Torque forces are transmitted from the shaft to the inner race by means of a keyway and from the outer race to the seat by means of front pullers. Shaft tolerances must be either h6 or j6, seating tolerances must be H7 or G7. If no front pullers are used, the seating tolerance becomes K6. Before being put onto service, the freewheels must be lubricated with suitable lubricants following the instructions given on page 12. Oil lubrication is essential when a high number of rotations in neutral is reached.