Just about any manufacturer will have a spine calculator on their site, you take the bow poundage, and the arrow length, and it calculates the spine (stiffness) of the arrow needed. Too stiff, or too flimsy, and the arrow will flex too little, or too much (parabolically) when released, effecting your accuracy to varying degrees. It pays to find the correct spine. You'll also need to consider the weight of the tips in this calculation (100 grain, 125, 85, etc...). Good luck!