Solid ruberwood unit building blocks encourage problem solving enhance social and perception skills promote shape and size recognition and teach basic math and science skills. Smooth sanded finish. 100% safe. All blocks are based on a unit measurement of 1 1/4. This base unit measurement gives each set complete uniformity for successful architecture. This set is a wonderful combination of tabletop size blocks and blocks that are a little bigger in size. The smallest block is 1 1/4L and the largest is 5 1/2L. See Pricing Here