"MATERIAL ALUMINUM ALLOY PLATE 6061-T651 PER QQ-A-250/11; ANODIZED PER MIL-A-8625,TYPE 3,CLASS 1; O/A DIM: 17 IN. SQUARE BY 2.062 IN. AT APEX OF SPHERE,0.625 IN. SMALLEST THICKNESS; 1 HOLE 0.844 IN. DIA IN CENTER CBORE 1.750 IN. DIA BY 1.062 IN. DEEP; 4 HOLES 0.190-32 UNF-2B BY 0.50 IN. MIN"