Size 3-7/8" X 7-3/4". 33 Circles from 1 to 25mm. Permanent pin-point centering. CIRCLE SWINGER feature is a series of .046 pin holes which can be used to draw much larger circles, all the way to 358mm. diameter. Increments of 2mm. are obtained by using different centers. Works with pencil or fine ball-point pen.