graphite shaft flexibility

Question
i am new to the world of club building and am trying to gain an overall knowledge of options to optimize design...i am aware of the various graphite flex designations, "L,A.R,S, and X-S."
occasionally i come across shafts that are labeled firm...where do these fit into these options?  thanks, (see you on the tour)

Answer
Ed,

Hope to see you on the tour. If you need a caddie, let me know.

The following are the different designation of shaft flex from the most flexible to the firmest.

Ladies, Seniors, Regular, Stiff and Extra Stiff. The firm category is similar to the stiff (s) category.

Hope this helps,

Michael Hoffman