THE BRIDGEPORT QUILLMASTER RIGHT ANGLE HEAD MILLING ATTACHMENT IS DESIGNED FOR R8 TOOLING. THE ATTACHMENT HAS AN OVERALL HEIGHT OF 6 1/2" (6.5" PER DESCRIPTION). THE BASE FEATURES AN INNER DIAMETER (ID) OF 3-3/8" AND AN OUTER DIAMETER (OD) OF 4". THE CENTER HEIGHT FROM THE BASE TO THE BIT IS 5-1/2".