Six strips of premium quality black and white erasing felt are dual sewn with heavy nylon thread to a rigid inner felt back. A comfortable, 1/8" felt back is then laminated and double lock-stitched creating a full 7/16" thick, non-breakable back. These features assure better cleaning and a longer life. Sold as Single Unit. Premium quality, value priced. Double sewn for strength. Six strips black and white felt provide better cleaning. Designed and built for long life.