Last year Tractor Supply had a 2-for deal on the 6ah flex-volt, bought them to back up the chainsaw 9ah, and the (2)10ah (non flex-volt) in the push mower. When it comes to Li, I only go with the mfr's stuff, not worth the small savings to risk burning down My Home. MAC Tools is the DeWalt hi-output stuff, if You come across any of their stuff.