What is an efficiency or MERV rating?
Most filters are labeled with a MERV (Minimum Efficiency Reporting Value) rating number, which measures a filter's ability to trap particles ranging in size from 3.0 microns to 10.0 microns. 

Residential filters commonly have MERV ratings of 1-11. The higher the MERV rating, the more efficient the filter is, and the more particles it can filter.
• A MERV rating of 6 means the filter is 35% to 50% minimum efficient at capturing particles, sized 3.0-10.0 microns.
• A MERV rating of 7 means the filter is 50% to 70% minimum efficient at capturing particles, sized 3.0-10.0 microns.
• A MERV rating of 8 means the filter is 70% minimum efficient at capturing particles, sized 3.0-10.0 microns.
• A MERV rating of 11 means the filter is 85% minimum efficient at capturing particles, sized 3.0-10.0 microns.

MERV is an industry standard rating, so it can be used to compare filters made by different companies.

Traditional fiberglass furnace air filters, such as the StrataDensity, are designed to protect sensitive heating and air conditioning equipment.  If you are wanting to improve your indoor air quality and capture smaller particulates, especially those related to allergies, then you should consider a higher efficiency, MERV 8 or MERV 11, pleated filter such as the PerfectPleat Ultra or AmAir 1100.

Filter Basics
Home air filters ­ also commonly called "furnace filters" ­ keep the coils and heat exchanges on the heating and air conditioning system clean. Dirty coils and heat exchanges make the system work harder, so keeping the filter clean helps prolong the life of your HVAC unit. 

Of course, the filters also clean the air that you and your family breathe. The variety and amount of particles in your home's air will depend on how many people and pets live in the house and what types of activities go on there. People with allergies or asthma should be extra diligent about keeping home air filters clean.  The most important thing to remember about home air filters is to change them regularly.

Generally, standard 1" depth fiberglass filters should be changed every 30 days and 1" depth pleated filters every 90 days. The filter life of a 2" and 4" depth filter is 4-6 months as they have more surface area to collect dust particles. However, recommendations vary based on a number of factors: the type of filter that you use, how many pets you have, whether anyone in your home has allergies, etc.  

It is recommend that you run your system fan continually for better air cleaning performance from your air filter. The air filter can only clean air that circulates through it.

My filter is an odd size is that unusual?  What is a Nominal Size?
In general, all standard filter sizes are stated according to their nominal size and not their actual size.  The nominal size represents the size of your filter rack.  The actual size represents the size your filter should be to fit inside your filter rack.  Typically, your filter is 1/4" to 1/2" smaller than your filter rack.  The nominal and actual size can be found on the side of your air filter.

For example, our standard size PerfectPleat Ultra 20 x 20 x 1 actually measures 19-1/2 x 19-1/2 x 3/4.  Sometimes, a home will have a special size filter rack to accommodate a certain square footage.  In this case, a standard sized filter will not fit and you will need to order a custom made filter. 

When ordering custom made filters please note that these filters will be made to your exact specifications ± 1/8 inch.  Therefore, please provide us with the exact actual width and length of the filter.  Please be sure to measure exactly for a snug fit to allow the filter to fit within the rack but without air seepage around the filter. 
Remember: custom made filters are not returnable.

Shipping and Returns?  All orders are processed Monday through Friday from 8am to 5pm excluding holidays.  We do our best to get your order out as soon as possible.  All in stock items ship out in 3-5 working days.  Custom made filters ship out within 10-15 working days. Custom made filters are not returnable.  If your order was damaged, defective or you received the wrong item you must notify us within 30 days from the date of delivery.  If you ordered a standard sized filter and you inadvertently ordered the wrong size please call or e-mail us for a product return number and shipping address.  To receive a refund or credit, you must ship the filters back to us within 30 days from the date of delivery. Filters must be unused to receive a refund or credit.  All returns are subject to a 10-15% restock fee.  If you return any items from an order that received FREE shipping, the original shipping savings associated with the returned item(s) will be deducted from the refund amount unless the return was due to our error.