12x16 Cluster Fiber Pillow Form Insert Complete your new bedding set with one or more of these sham stuffers Made from 100% cluster fiber fiber filling Considered to be one of the smoothest most lump free fibers available, cluster fiber consists of thousands of individual cluster balls inside each pillow which are free to move around and rearrange inside the pillow. This increases the life of the pillow since no particular section will matt down. Cluster fiber is also softer than traditional fiber and last up to 2 - 4 years longer.