HEPA Filter for Silento 12 litter and 20 litter quiet vacuums. This very large filter has the advantage to be washable. Put it under cold or lukewarm water. Use a paint brush (DON’T use harsh scrubbing brush because you’ll damage the fabric with it) and gently brush filter under the water. As for the size, the larger the filter the better the operator is off because it need to change infrequently. Less time to change mean less money to spend. This is why the initial cost of the machine is higher than the competitors.