Replace your synthetic poly prefilter with our wonderful Organic Wool or ecowool prefilter. We can make these to fit any air filter. 
These filters are 1/4" thick of airy lightly felted wool. 
I have also used these under my sink drying rack to prevent mold buildup. I use the scraps for scrubbing and cleaning my kitchen. 
 
Organic Wool comes from foreign sheep that are certified GOTS Organic and is processed according to GOTS standards right here in California. 

EcoWool is taken from healthy living organically raised Northern California sheep and processed without any additives. As pure as organic wool and processed at the same organic wool plant here in California. Sheep wool insulation is an outstanding insulator. For thousands of years sheep have been able to survive the elements using their wool coats to protect them from extreme cold and heat. ... Thermal conductivity is the ability for heat to pass from one side of a material through to the other.
Additionally, recent research shows wool helps detox the air by trapping toxic vocs. Someday I hope we all get to have wool insulation in our walls. 
I have made these for my air filters as well. 
These will have a slight natural wool odor as the smell is from the natural oils and will dissipate over time. 
These can be made any custom size. Contact us for your size.
 
Made in USA by Healthy Body Head To Toe, Fine Organics since 1992
 
The 13.5 x 53 is for the Austin Air Filters to replace the polyester prefilter.
11 x 39 is for the Austin Air Junior Models