THIS NIKKEN EC45-12 END MILL HOLDER IS A CAT 45 TYPE TOOLING. ITS OVERALL LENGTH (OAL) IS 4-3/4 INCHES, AND IT FEATURES A BORE DIAMETER OF 1/2 INCH. THE BODY DIAMETER MEASURES 1.50 INCHES, AND THE PROJECTION IS 1-1/4 INCHES. THE PART NUMBER FOR THIS HOLDER IS EC45-1/2".