The small one on the left is a 650mah eGo-C replacement battery. The long one on the right is the new eGo-C Twist 1000mah. It works really well. I've brought my old eGo-T atomizers back to life with this 1000mah twist set at 4.0 v. I'm loving my 1000mah twist. Just wanted to show you the size of it.