These were a purchase for me by the USAF to do blasting cap workups safely. They were a special order, and had prescription lenses glued into small cutouts in the original Strike lenses; a fine idea to be sure, but unfortunately the original lens was narrowed and weakened by the cutouts and the stress that's normally on M Frame lenses (just the simple spring bending that keeps them in the frames) caused them to crack along the bottom and the prescription lenses to fall out. I replaced the prescription lenses with a new stock black iridium Strike lens, along with yellow (for shooting) and clear (for overcast sky and night time cap workups) lenses within a year or so after the original purchase. These, along with the rest of my collection was lost when I moved from Detroit to Fort Wayne. **I included a picture of the clear lenses with prescription inserts so you could see what I meant. The cracks would develop along the bottoms of the lens, running top to bottom, and would go all the way through to the prescriptions, causing them to come out.**