Solid poplar construction, these blocks will withstand years of hard use. Smoothly sanded for safe play. Each block is precisely related in size to the basic unit block (5-1/2"L x 2-3/4"W x 1-3/4"D). The unit block system makes it easy for children to understand size relationships and develop skills through block play. Encourages cooperative play. Children will amaze themselves with their imaginative creations. Sets feature 23 different shapes. Greenguard? Certified. Lifetime warranty.