TNK is an Italian company that produces replacement fork stanchions for all types of motorcycles on the market. TNK fork tubes are OEM quality replacements. Not only are they the highest quality, they are generally significantly less expensive than original equipment. 

These are 41mm diameter and use the fork oil seal SUA66225. 

Please note, this stanchion does not include the fork top o-ring SUA74776 or the top screw.