The stretch needed for a call depends on a number of factors,...the thickness of the latex used, layers of reeds, spacing of reeds, and the cuts put in the call. Generally speaking, thinner latex material requires less stretch than thicker material to achieve the proper call tone qualities. Rasp in a call is more often a function of the cuts in the reed(s) than the stretch, although the other variables mentioned above do play a role, as well.
