Sturmey-Archer Sprocket Spacer 1.7 mm - 1/16"

Two of these go onto the driver along with the sprocket and the sprocket dust cap.

The spacers may be re-arranged to allow you to fine-tune the chain line.

These spacers are also sometimes used under the fixed cup of a bottom bracket, or under a thread-on freewheel or track sprocket, to correct chainline or other problems.

Click here for a parts diagram of the Sturmey-Archer AW hub.