THE BISON 4344 IS A 4 JAW CHUCK WITH AN OVERALL DIAMETER OF 15.75 INCHES, DESIGNED FOR LATHE APPLICATIONS. IT FEATURES A D1-8 BACKPLATE AND HAS A CENTER HOLE MEASURING 4 INCHES. THE THICKNESS OF THE CHUCK IS 4 INCHES. THIS UNIT UTILIZES 6 PINS, EACH MEASURING 1 INCH. AN ADDITIONAL SPECIFICATION NOTES A 5.5-INCH CENTER HOLE.