Steelex D3607 4-Inch 3-Jaw Chuck 4 inch; 3-jaw; plain back Inside jaw minimum/maximum jaw openings are .08 to 1.181 inches / 1.181 to 3.543 inches Outside jaw minimum/maximum openings are 1.181 to 3.150 inches Outside jaw minimum/maximum openings are 1.181 to 3.150 inches Precision ground components