Good morning, Ron W;
Ron LarFor4X5's comment is valid. You will find that the Vivitar Series One 90mm f2.5 lens is a very good lens. I have it with the 1:1 adapter, and it has served me very well in making photographs of small parts for projection onto large screens for big audiences to see the way that I am putting together a system. This lens is right in there with the Vivitar Series One 2.8/105, the Tamron SP 2.8/90 (both of those are here also), and the Lester Dine equivalents. Kino Precision (Kiron) got this one right.
Enjoy; Ralph, Latte Land, Washington