A Trane Envirowise replacement air filter is an integral part of a whole home comfort system that protects your equipment as well as your family by filtering dust and allergens from the air you breathe. Only used with the Quikbox filter box , these Envirowise filters can last up to 6 months and is easily replaceable by you or your installer.American Standard / Trane / Service First Part # FLRQB5FR21M11 , up to 6 Month Filter Life Specifications: OEM Expandable Media Filter , Approx. dimensions: 21 x 26 x 5 / 20.2x26x4.7 , MERV11 ,These Filters are ONLY USED with American Standard or Trane QuikBox Housings , Images Shown for Illustration OnlyReplaces / Supersedes: 20.2 x 26 x 4.7 21x26x5 FLRQB5FR21M11 QwikBox EnviroWise Qwik Box Quikbox Quik Enviro Wise Filters FLRQB5FR FLRQB5FR21 DTRFLRQB5FR21M11 and others