This is the factory original OEM True H13 class HEPA filter (Neutralizer) for the two speed E2 Type 12 (Black, Silver, e2 Gold) version Rainbow vacuum. If you only have an on and off switch and not a hi and low speed, then this filter IS NOT compatible.
You should replace your filter once every 4-6 years. If you need to replace it more often, you should change your water basin in the middle of cleaning. Once the water gets thick with dirt and debris, it becomes more difficult to filter. The dirt will start to bounce off the sludge and go up through the motor and get caught by the HEPA filter.
Be careful not to vacuum up drywall dust or baby powder as the water has a difficult time filtering this type of material.
Effective serial number 1000000 with a start date of September 4th 2003 through current production. The bulk item number for this is R12647B. Some websites list this part number for a single item which is incorrect.
It is better to toss your old filter and not replace it than to buy a generic filter. Generic filters do very little for the air quality while reducing your airflow and performance.