{"product_id":"21x21x5-air-filter-merv-11-superior-pet-allergy-defense-reliable","title":"21x21x5 Air Filter MERV 11 Superior Pet \u0026 Allergy Defense - Reliable","description":"\u003cp\u003eOur review of this 21x21x5 air filter finds it best suited for homeowners and small businesses that need a durable, higher-performance replacement for furnace or HVAC systems. The single biggest reason to buy is the \u003cstrong\u003eMERV 11 performance\u003c\/strong\u003e, which captures a high percentage of airborne dust and pet dander without significantly restricting airflow. Installation is straightforward and the build quality - recyclable beverage board frame with dual wire backing - feels noticeably sturdier than basic cardboard options, which matters if your filter sits in a hot or humid cabinet.\u003c\/p\u003e\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eWhole house replacement:\u003c\/strong\u003e The nominal 21x21x5 size (actual 20.63 in x 20.63 in x 4.38 in) fits common furnace and air handler slots to protect an entire HVAC system.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMERV 11 filtration:\u003c\/strong\u003e Synthetic media rated as MERV 11 (comparable to MPR 1200 and FPR 7) captures a high portion of allergens, dust, and pet hair while maintaining steady airflow.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eElectrostatic pleated media:\u003c\/strong\u003e Eight pleats per ft and electrostatic charge trap more microscopic particles than fiberglass pads and extend usable life.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDurable frame:\u003c\/strong\u003e Beverage board frame with dual wire backing resists warping and stands up to temperature changes better than basic cardboard designs.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMade in the USA media:\u003c\/strong\u003e The synthetic filter media is produced domestically, supporting consistent quality and reliable electrostatic charge.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eWho It's For\u003c\/h2\u003e\n\u003cp\u003eThis filter is ideal for homeowners with pets or allergy sufferers who want better particle capture than standard fiberglass filters without a big hit to airflow. It also fits customers using Rheem, Ruud, or Protech housings who need a direct-fit replacement that lasts longer than thin disposable pads.\u003c\/p\u003e\n\u003cp\u003eThose with ultra-sensitive medical needs or who require hospital-grade filtration should look at higher MERV levels or specialized filters. If you have a nonstandard filter slot or require exact factory OEM branding, verify compatibility with your model numbers before purchasing.\u003c\/p\u003e\n\u003ch2\u003ePros \u0026amp; Cons\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003ePros\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eGood balance of filtration and airflow thanks to \u003cstrong\u003eMERV 11\u003c\/strong\u003e synthetic media.\u003c\/li\u003e\n\u003cli\u003eLasts longer than fiberglass filters due to electrostatic charge and pleat density.\u003c\/li\u003e\n\u003cli\u003eSturdy beverage board frame with dual wire backing improves durability and ease of installation.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eCons\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eRecommended replacement every 90 days, so ongoing cost is higher than very cheap fiberglass pads.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch2\u003eSpecifications\u003c\/h2\u003e\n\u003ctable\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eFilterbuy\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNominal size\u003c\/td\u003e\n\u003ctd\u003e21x21x5 in\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eActual size\u003c\/td\u003e\n\u003ctd\u003e20.63 in x 20.63 in x 4.38 in\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFilter rating\u003c\/td\u003e\n\u003ctd\u003eMERV 11 (comparable to MPR 1200, FPR 7)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMedia\u003c\/td\u003e\n\u003ctd\u003eElectrostatically charged synthetic media, made in the USA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFrame\u003c\/td\u003e\n\u003ctd\u003eRecyclable beverage board with dual wire backing\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRecommended replacement\u003c\/td\u003e\n\u003ctd\u003eEvery 90 days\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\n\u003ch2\u003eOur Verdict\u003c\/h2\u003e\n\u003cp\u003eFor most homeowners with pets or seasonal allergies, this 21x21x5 MERV 11 filter is a practical upgrade over fiberglass pads, offering better particle capture, a robust frame, and longer life per filter. It is good value for those who prioritize cleaner air and reliable fit in Rheem, Ruud, and Protech compatible housings.\u003c\/p\u003e\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003cp\u003e\u003cstrong\u003eWill this filter fit Rheem and Ruud housings?\u003c\/strong\u003e\u003cbr\u003eYes, it is compatible with Rheem and Ruud filter part numbers and common housing models stated for 21x21x5 slots.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eHow often should it be replaced?\u003c\/strong\u003e\u003cbr\u003eThe manufacturer recommends replacing the filter every 90 days for best performance.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eDoes the MERV 11 rating restrict airflow?\u003c\/strong\u003e\u003cbr\u003eMERV 11 captures more particles than fiberglass while still allowing steady airflow suitable for most residential HVAC systems.\u003c\/p\u003e","brand":"Filterbuy","offers":[{"title":"Default Title","offer_id":48202598318299,"sku":"B07RYWNVHJ","price":70.08,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0724\/1043\/1707\/files\/71jsCqkDJuL._AC_SL1500_0752e108-be89-4f3d-96ed-6c23669dbbe3.jpg?v=1770303441","url":"https:\/\/gearmusthave.com\/products\/21x21x5-air-filter-merv-11-superior-pet-allergy-defense-reliable","provider":"GearMustHave","version":"1.0","type":"link"}