The Screw 6x16 is the lowest priced item on this Water Pump schematic.
Parts such as the Water Pump: Washer, O Ring,water Pump Holder, Shaft, Bolt are included in the Gsxr600 2001 (k1) Usa (e03) Water Pump parts fiche.
This WATER PUMP assembly utilises two Screw 6x16(s) - the highest specified component.