Coremat® 4mm 39.37". Coremat is a random laid, shredded polyester material, which is soft in nature and conforms well. This materials is used for creating bulk in a laminate as well as controlling print. Using this material as a core is a cheaper alternative to solid fiber parts and the use of the core will add rigidity. The material is 39.37" wide and is 4mm thick. The coremat is sold by the yard.