100% Polyester
The fuzzy strip is sewn on theWindowBlanket. This attaches to the sticky back sill strip that adheres to the top of your windowsill frame.  Some customers prefer a white sticky back sill strip if their windowsill is white.  However, since the sticky back sill strip is placed on the upper side of the top windowsill, it may not be noticable and again depends on your window style.  The purpose of theWindowBlanket is to insulate and/or block out light. It usually mounts behind your usual window treatments and is easily removed.