Unfortunately, it's not that simple. Why would I, or anyone want s1's of a strain if F1's are still available? Why would someone make s1's of a strain if f1's are available? Every S1 seed I've ever had is from a verified cut of a strain that can no longer be made and/or is incredibly hard to get your hands on.. Like gg4 s1's, geisel s1, crippy s1's ect. The person you are dealing with may have their terminology wrong.. Maybe they mean that they have f1 regs of a strain and that they reversed a plant to make a fem version of the strain, and that he has a reg version and a fem version.. But who knows. In this case I'd take whatever he is calling the f1's, lol.