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TopTech TechPure TT-FM-2025 QB OEM 20x25x4 Replacement Furnace Filter - QwikBox(R)

Size Guide

TopTech TT-FM-2025 20x25x4 furnace filters are designed for the TechPure TT-MAC-2522 & TT-MAC-2025 air cleaners. They are rated at MERV 11 and remove many allergens, dust, pollen and other airborne pollutants. The new QwikBox(R) collapsed design provides for less chance of shipping damage and takes up less space so it is more convenient to keep spare filters on hand. Assembly required. 

  • New QwikBox(R) Collapsed Design That Is Easy To Assemble Prior to Installation
  • MERV 11
  • TopTech TechPure OEM Original Equipment Replacement Air Filter
  • Fits TechPure TT-MAC-2522 & TT-MAC-2025 Air Cleaners
  • Actual Size 19.375" x 24.375" x 3.75"
  • initial resistance .232
  • Maximum Air Flow 500fpm

Customer Reviews

Based on 20 reviews
Perfect Fit

Very fast service. Was exactly the dimensions requested as opposed to purchase at a big box store that was not the the exact size printed on the box - when I got home I saw in very fine print that it was actually slightly bigger and would not fit. Will buy from this supplier again.

Happy to have found Atomic Filters

The transaction was smooth and delivery quick. I have not installed the filter, yet, but I am pleased with the purchase process and plan to return to Atomic Filters for future purchases.

First time order

Was very pleased with delivery speed. Easy to install.

Fair price with quick delivery

Found out the hard way not to buy according to nominal size. This is the correct filter for my unit. Shipped in timely fashion and arrived a day earlier than expected. Only quibble is that I thought I was ordering a QwikBox but received fully assembled unit. That isn't necessarily a problem but I want to buy a few to have on hand and the QwikBox filters store in less space.

Easy to order; quick delivery

Couldn't find the exact actual size at local store. All 20x25x4 filters are not the same. Found the exact replacement at Atomic Filters, ordered them and had them within a few days!

Nominal Vs. Actual Sizes: Finding the Right Air Filter Size

Buying the Correct Size Air Filter- The Most Important Thing to Know 

When you are buying your air filter online most important thing to know is Air Filters have two sizes that you need to understand the Nominal size and the Actual Size. Not understanding these numbers often leads to consumers purchasing a filter that does not fit their Furnace or HVAC system. See the complete list of Air Filters by Size Rating and Brand.

Nominal vs Actual air filter size by Atomic


Understanding Nominal Filters Size Could Save You Time and Money

Not understanding the Nominal Filter Size is the primary culprit for incorrectly purchased filters.The Nominal Size is the usually the dimensions used to Label the filter. For instance 16x20x1. These dimensions are a rounded value on the filters actual measurements. The actual measurements on this filter may be 15.5x19.5x.75, but that could vary by brand and manufacturer. So in order to make sure you have the correct size filter, especially if you are replacing with a different brand it is important to confirm the actual size on the filter. When purchasing filters on the internet the Nominal size is usually found in the product title.

Actual Filter Size- The Key to Making the Right Replacement Filter Purchase

The actual size as you might have guessed are the actual dimensions of the filter by length, width and thickness. This size is often on the filter right below the Nominal size and is usually labeled as the actual size. When you are buying a filter online the actual size is sometime in the product bullet point or the product description. If your filter does not have actual dimensions on the outside of the filter, you can measure you filter to get the correct dimensions. Some brands have a foam gasket on the outside of the filter, in this case, you will want to make sure you have a compatible actual size and that it also has the foam to ensure a snug fit. 

Lennox Air Filter X0851 with Foam strips

Examples of Nominal and Actual Sizes

 Size  Example 1  Example 2
Nominal Size 20x20x1 16x20x1
Actual Size 19.5x19.5x.75 15.75x19.75x.75


 Furnace filters should fit securely but should not have to be forced into position. If you have to force the filter into its slot, then it is probably too big. Forcing an improper filter size in a filter can cause it to buckle, damaging the filter or reducing its ability to function properly. Filters are a smaller than their slot to allow for easy replacement. Some HVAC units may need a filter with dimensions that are unique or uncommon. In these cases, a custom filter needs to be ordered.

Find Your Filter Sizes Easy in 1" Deep Filters , 2" Deep Filters, 4" Deep Filters