This is the steam nozzle base O-ring (SW type) for Asahi Kasei's pressure cooker "Katsuryoku Nabe (SW type)". This is a used part removed from a SW 5.5L pot manufactured in 2005. There are no noticeable stains or scratches. This is a common part for the 5.5L and 3.0L sizes of the SW type. The shape and size are different from the current mainstream ZK type and cannot be used interchangeably. Asahi Kasei Katsuryoku Nabe Parts