Cork is a renewable, sustainable material, which comes from the bark of a Cork Oak Tree. There are no toxic chemicals used in the manufacturing process. The Cork Block sets the standard for high performance yoga props. Cork is a renewable, sustainable material, which comes from the bark of a Cork Oak Tree. It has a firmness not found in foam blocks, & means that you can feel secure in the support it provides. The smooth rounded edges & corners provide added comfort & an easier hand grip. Why the Fushi Expert panel like it Sturdy, no give but still so light!