Many people don't realize how important finding the correct arrow spine is. There are also a few people who have probably never even heard of this. Putting it in simple terms, spine is basically how much the arrow "flexes". When shooting a longer draw length and heavier poundage, you need a stiffer arrow, or in other words, an arrow that flexes less. To find out what spine arrow you should be shooting out of your bow, just about every arrow manufacturer offers a spine chart on their website. All you need to do is know your poundage, draw length, and point weight and they will give you the arrow that will be properly fitted for you. This is a very important step when trying to achieve better accuracy.