The straightness of an arrow is just what it sounds like, and it's usually expressed in plus or minus a few thousandths of an inch.  A perfectly straight arrow (if that were to exist) would be a ±.000" arrow.  All other others are "crooked" to some small measure.  But don't worry ... we're literally talking about splitting hairs.  A basic arrow will usually have an advertised straightness of ±.006", and a premium arrow as little as ±.001".  Oddly enough, that's about the thickness range of human hair.  So even if you buy the "most crooked" arrow on our list, it's still straight to the whisker width.  Per ATA/ASTM standards, arrow straightness should be measured along the full length of the shaft minus two inches.  However, measuring a ±.001" deviation along a 30" section of a flexible cylinder requires some pretty specialized equipment.  So this is one specification that's hard to verify. 

And perhaps it's worth noting the obvious ... the straighter an arrow is, the more money they charge for it.  So as an established retailer representing these fine products, we officially recommend that you buy the straightest arrow you can afford.  Off the record, we suspect that a ±.001" arrow straightness is more about targeting your wallet than your deer.  There ... we said it.  If you need help, call our pro-shop at 877-410-7811 or email us for assistance.

I'm still confused.  Give me the full lesson from the top!