VihtaVuori is a Finnish Powder Company that has been manufacturing powder since the 1920's. VihtaVuori powders are extremely popular with benchrest shooters, High Power shooters, and varmint hunters.
This powder is a hybrid of single and double based powders. The result produces a velocity increase of 5 to 10 percent while pressure levels remain the same. For most rifle cartridges this increase will be approximately 100-200 fps.
Big Book Catalog, Issue:67, Page:527
Sinclair, Issue:4B, Page:094