【ADVANTAGE OF OUR CHARCOAL FILTERS】 Insert our activated charcoal air filter into the air vent registers to purify the air coming from your AC units and heaters 【PACKAGE CONTENTS】 14 Pack of 4" x 12" Activated Charcoal Carbon Air Filter Sheet for home 4 x 12 Inch 【DIMENSION】 4x12 inches. Easily trimmed with scissors to the size you need. Our newest activated carbon filter has been thickened and its density has been increased by approximately two times, thereby increasing the odor elimination effect by 50%. 【COMPATIBLE WITH】 Floor, wall, ceiling, and baseboard register & grilles in bedrooms, offices, schools, hospitals, or any living space 【REPLACEMENT TIME】 For best performance, it is recommended to replace the charcoal filter every 3-6 months Floor Vent Filters, Air Vent Filters for Home 4" x 12" Breathe green, be thankful for life What is in the box:4" x 12" Premium Register Air Filters, total 14 packs.Design: ①✂️ Easily trimmed with scissors to the size you need. ② Thickened: Our newest register filter has been thickened and its density has been increased by approximately two times Tips: Replacement Time: for best performance, it is recommended to replace the carbon filter every 3-6 months.