SL9139 Mini 2 in. x 4 in. Blackboard pkg/12 2 in. x 4 in. is the measurement of the blackboard with an additional 1/8 in. wooden frame and hanger. Blackboards have a blackboard surface on one side and plain wood on the back. Best used for decorative painting. You may paint or use a permanent marker on these boards. Use for signs or Instructions. Customer comments that writing with chalk, erasing then rewriting does not work well.