Our Dry Erase Fact Family Triangles are double sided with a focus on the relationship between subtraction and addition on one side and on the relationship between division and multiplication on the opposite side. We have made our 10" triangle flash cards using very durable Sintra PVC Foam and we combined that with dry erase lamination so that we could offer you a lifetime warranty. Proudly Made In The U.S.A. This resource is great for students in Kindergarten thru 5th grade. Building math skills is important and that's a FACT!