We know buying replacement filters for your home or business can be a challenge, especially if it's your first time. That's why we offer our Purchase Guarantee. We make your purchase risk free with these features.
The Honeywell TR21 that you're looking for is no longer available for sale.
If you have a 6-month filter, schedule your filter changes when daylight savings changes. When you "spring forward" or "fall back" setting clocks around the house, change your filter at the same time.