THIS IS A JACOBS TAPER CHUCK, MODEL 36 PD – 3 TAPER, COMPATIBLE WITH A CAT 50 HOLDER TYPE. THE CHUCK HAS A CAPACITY RANGE OF .18 - .80 INCHES OR 5-20 MILLIMETERS, SUITABLE FOR COMPATIBLE DRILL DIAMETERS FROM 3/16 INCH MINIMUM UP TO 51/64 INCH MAXIMUM. THE OVERALL LENGTH (OAL) MEASURES 9.5 INCHES, WITH A PROJECTION OF 5.5 INCHES. THE MAXIMUM OUTSIDE DIAMETER IS 2.54 INCHES.