This cone-like shape bur/Mini mandrel holder and organizer is a great tool that helps you organize and hold all your burs on top of your benchtop for easy access. This unit has a total of 246 holes: 192 openings for the standard quick release burs and mini mandrels (standard shank size 2.38mm or 3/32" or 0.094inches). 48 openings for the large burs/mini mandrels with a thicker shank (3.17mm or 1/8" or 0.125inches). 6 openings on the top to hold the GRS quick-change engraver holder, or they can be used to hold miscellaneous burs and mini mandrels. The unit sits on ball bearing gliders which allows 360 rotation with ease.