Made of Billit tempered 6061T6 aluminum. Machined one piece design. Installation requires no special tools. Perfect ring alignment - no lapping required. Full 1/2 inch thread length in rings. MOA Mounts are tapered down on front for long range shooting. Height will be about .03" lower on front ring than a standard mount. Base screws are 6-48 X 1/4" long. Ring screws are 6-40 X 5/8" long. Both use a 7/64" Allen wrench. Some of the .338 Lapua receivers have been modified at the factory and have larger base screws. The size of them is 8-40 and will use a 9/64 Allen wrench.