This Transparent Geoboard is 9" x 9" in measure & can be used on overhead projector. This Geoboard ( Transparent) has 11 x 11 peg grid. The knobbed pins hold rubber bands (included) in place. The Geoboard is primarily used in the exploration and recognition of shapes, designs, spatial relationships, angles, fractions, area, perimeter, symmetry, and coordinates. It is suitable for ages 5 to 13.