NO AIR in this rug pad like in other 32 ounce pads! Ours is 3/8" Thick ALL FELT, making it MOST DENSE! * OTHERS HAVE AN ADHESIVE COATING, NOT OURS! This means it will NOT off-gas or stain your floors! * SUPREME 32 OUNCE(TM) 100% Recycled Felt Rug Pads do not contain rubber, so do not prevent slipping. They are excellent for sound reduction, making them a great choice for use in apartments * SUPREME 32 OUNCE(TM) 100% Recycled Felt Rug Pads are naturally hypo-allergenic, mold, mildew, and moth resistant * SUPREME 32 OUNCE(TM) 100% Recycled Felt Rug Pads are guaranteed for 15 years. They do not contain glues, latex, rubber or adhesives and will NOT mark or stain your floors.