Material for inlet covers shall have the following chemical composition: 67-71 pct copper with zinc remainder; 5.34 in. Long; 3.788 in. Inside dia; 0.031 in thickness all around; 72.0 in. Radius; 0.38 in. Nose circumference; inlet cover used for 8 inch 55 caliber projectile mk 21 all mods or mk 23 all mods