At special request:
Mudd they are :
75's =.600 spine = aproxiamtely 44 #'s and down
(good for really light weight bows even though they may not be perfect for the 20 -35# bows, they will work with field points.
90's = .530spine = good for weights from 40 - 50 # bows
150's= .487 spine = good for bows from 48 - 56 #'s
250's= .373 spine = good for bows from 55 - 65 #'s
350's= .320 spine. = for bows from 62 - 80 #'s
this is a general description. This will vary some due to draw length, length of shaft, weight up front, and how deeply the shelf is cut. There are also the ocasional exception to the rule shooting a 350 out of a 45# bow so there is no set in stone rule.
Also, if you don't plan on shooting anything but field tips, it is not nearly as critical to be perfectly tuned.
Bigjim
Now you know.
thanks,bigjim