This is the micrometer adjustment mount set for the Malcolm 8X USMC Sniper. This mounting kit will also work for the Malcolm 3X and 6X Short Telescopic Sights.
The M8USMCMT set includes:
2 x 1/2" wide 60 degree type bases
1 x Front Mount
1 x Adjustable Micrometer Rear Mount
1 x Front Lock Ring
M8USMC Mount Instructional Manual [download]