Smart Poly® material has been designed for charts in the classroom and home. Write-on/wipe-off heavy duty washable all poly chart, no lamination needed. Material is designed to be long lasting, easy to clean, waterproof, and durable for many years of use. Use with dry erase or water based markers and washable crayons for interactive play and educational development. Use with Ashley Smart Tak®, pins, tacks, staples, etc. to hang in the classroom. Great for reusable learning. Classroom Essentials Charts measure 17" x 22" with a dry-erase, glossy surface, .45mm. Each set includes 4 charts.