These “Picatinny” style bases by Ken Farrell are CNC machined and are available in a two-piece set. The bases are made in a standard configuration (no taper) or with a 20 MOA taper, which allows a shooter to keep his scope more optically centered when shooting longer yardages. Some scopes, when mounted on conventional bases, do not have enough elevation adjustment for longer yardages or are at the very end of their adjustment range.
Big Book Catalog, Issue:66, Page:250
New Product Supplement, Issue:562, Page:005
Sinclair, Issue:3B, Page:206