Slow Speed Latch-type with push button equipped with 4-hole connector. The hole size is 2.3 mm and is designed to be used with polishing mandrels and abrasives, like Jiffy Cups, and OptiDiscs. Use of the slow speed with polishers and discs will allow you to create smooth tooth surfaces and repair adjacent tooth damage. See: Emergency Repair Kit. This is a low priced item and will be tested for proper function by Dr. Stevenson, but has no guarantee.