THIS IS A BISON 4 JAW CHUCK WITH A D1-6 BACKPLATE. THE OVERALL DIAMETER OF THE CHUCK IS 10 INCHES, WITH A 3-INCH CENTER HOLE AND 3-INCH THICKNESS. THE BACKPLATE TYPE IS D1-6. IT FEATURES 6 TOTAL PINS, EACH MEASURING 0.875 INCHES. THE OUTER CENTER HOLE DIAMETER IS 4 INCHES. A WRENCH IS NOT INCLUDED WITH THIS ITEM.