47 blocks ranging from 1mm to 100mm. Each block has its opposing faces dead flat and finely polished. So much so that when one is gently rubbed against another the surfaces literally 'stick' to each other as if magnetised. The range includes 1mm to 1.19mm x .01mm, (plus 1.005mm), 1.2mm to 1.9mm x .1mm, 2mm to 9mm x 1mm and 10mm to 100mm x 10mm. All the blocks are supplied individually wrapped for protection and the set comes in a polished, fitted wooden case. Each set is also supplied with a certificate of accuracy to DIN861 grade 1 standard.