I hesitate to be the first one to answer this query, although others have admitted to buying ready-made reeds on other sections of this forum. I do not consider gsp blanks as ready-to-play, and certainly I would not have my students(or myself ) buy them as such.
Through more than 40 years of medical training and practice, I had no time to make my own reeds (even from blanks), and so have played on reeds from Nielsen Woodwinds for virtually all those years. I recommend them for my students, and instruct them in the techniques of adjusting the various varieties Nielsen sells. AND -- I use them myself for all teaching, practice, and performance situations.
I don't think I'm alone in this situation, and would love to have others who play ready-made reeds comment on this thread.
Dr. Bill Dawson, bassoonist and teacher
IDRS medical consultant
Past President, Performing Arts Medicine Assoc.
Author of "Fit as a Fiddle: The Musician's Guide to Playing Healthy"