"ANODIZE FINISH PER MIL-STD-171,COLOR BLACK,MADE FROM PART NO 10179400,MOUNT WIDTH IS 2.187,2 HOLES NO 6 /.138/-UNC-2B TO .375 IN. DEEP,NO 4 /112/-40UNC-2B HELICAL INSERT PER MS33646 1.500 IN. DIA DEEP 2 HOLES,1 HOLE 0.250 IN. 20 UNC-2B,1 HOLE 0.312 IN. 18-UNC 2B,DIA OF MOUNTING GROOVE IS 0.5008-0.5012 IN. DIA."