Grizzly 145045 3-Jaw Chuck for 4-Inch Rotary Table, 3-1/4-Inch Horizontal or vertical use 4- 5/16-Inch t-slots 1:72 ratio or 5 per revolution venire scale reads to 10 seconds 3 dividing plates sector arms 4- 5/16-Inch t-slots 1:72 ratio or 5 per revolution