Nominal Size: 20 x 30 x 1, Actual Size: 19 5/8 x 29 5/8 x 3/4 (19.63 x 29.63 x 0.75) Measure your air filter for the exact size and compare it to our actual size to ensure proper fit. Made with MERV rated synthetic poly blend pleated media Nordic Pure recommends changing 1" air filters every 30-90 days Made in the USA: Proudly manufactured in the USA, ensuring quality and supporting local production Ideal for customers with health problems or for commercial units which support a rating of MERV 14 and above