Cork Borers Set of 12. Inside Bore Sizes as follows: 18.25mm, 16.4mm, 14.2mm, 13.8mm, 12mm, 10.7mm, 9.3mm, 7.6mm, 5.5mm, 5.2mm, 4.9mm, 3.5mm. Used to cut hole in cork or rubber stopper to insert glass tubing.  Also used to take samples for experiments and punch holes on an agar plate. Overall length: 100mm