Arrow shaft 'spine'...
Good Morning,
Arrow shafts are sized/selected based on a numeric value indicative of their 'spine'. The challenge is that while there is an industry standard (as developed by Easton archery) not all of the arrow shaft manufacturers us it to boldly label their arrow shafts. In archery, spine = the amount of shaft deflection when a set weight (1.94 lb) is suspended from the mid-point of the shaft, with the shaft resting on two supports spaced 28" apart. A 500 spine arrow would have a deflection of 0.500" when tested using the criteria mentioned, a 350 spine arrow would deflect 0.350", and so on.
For our use, you are obviously going to want to select the lowest spine (shaft most resistant to bending) which you can find...
r/
Dave