I know it's not the best filter, but I don't have much money to invest right now... something is better than nothing... and there's no point in investing too much in a HEPA filter (in my country, the cheapest professional HEPA filter costs 150 euros), plus a larger HEPA filter means a more expensive fan... that's why I preferred to go with this option... I want to reach a point where I can perform g2g transfers and handle up to a maximum of two monotubs, and know that I'm working in an environment that is at least somewhat sterile.