This set includes a friction block and a friction board, both made of high quality, smoothly finished pine wood.� The friction block has a hook for a spring scale and three compartments for additional weights.� It can be placed face-up or sideways.� Students can vary the weight or area of contact to test their impact on the frictional force.� The set comes with three 50g weights and a 100g spring scale.� The board is 20" x 2" and the block is 4" x 1.5" x 1".� Includes an activity guide