Originally posted by ChuckC: To answer..... necessary ? No You can shoot arrows that are way different from each other and have fun. It is a tool. It helps you make better equipment which gives you the opportunity to excel. But... remember, although a super accurate tester will give you lots of info, even a cheap homemade version could give you all the info you need. Find an arrow that works well on your bow, test it and mark the deflection. Who cares what it means. Now find shafts that are close to that deflection and you are in the game.Like many hobbies, you can get in for cheap and dally, or you can go in way over your head and tread water. You choice, and that choice can ( and likely will) change over time.ChuckC