If you are planning to purchase a used aluminum bat soon,you can make sure the barrrel has no flat spots by simply placing a nylon/silky type cloth on your the palm of your hand,then place the barrel of the bat on the cloth,lightly grip the bat barrel and rotate the handle,as the barrel turns in your hand ,any flat spots will be felt instanly,the next step for a bat that has flat spots is cracking,so check the bat carefully I even look away from the barrel,so my hand does the "looking" for me,,some bats can look great and like new but have oval or flat spots on the barrel from not rotating the bat while hittng a ball ,especially if the bat is used at the cages..the nylon cloth will also detect any nicks or cracks,it'll snag on any defects..I hope this helps you with your next bat purchase,thanx "zman5775" vote if this was helpful ..PLAY BALL!!!