The Gsx600f Katana 2001 (k1) Usa (e03) Seat (model Y/k1/k2) consists of sixteen pieces with the Seat Assembly being the most expensive.
On this parts fiche the Cushion,seat(40x20x15) is the most specified component.
Some items from this specific schematic: Handle,pillion Rider, Bracket,seat Lock, Cushion,rider Hndl(17x24x1.5), Handle,pillion Rider.