Riccardi Apo Reducer 0.75

Is the Riccardi Apo Reducer 0.75 focal length limited (f/9 and below) or will it work on an f/12 refractor?

Reducers are either specifically designed for a certain scope or the manufacturer advises of a range the reducer will work with, helps the ROI. For example f/4 through f/7.5 sort of thing. I doubt the reducer will work with an f/12 refractor, much to far out of workable range and I could be wrong, but f/12 sounds like an achromat. Further, I believe the Riccardi .75 reducer is designed for apochromats, hence the Apo in the description and yes I also believe it's for f/9 or below scopes.