I had an older 40v Kobalt with a traditional "bump" style head and it worked fine - just like any regular ol' weedeater. After 7-8 years of hard use, I finally wore that weedeater out to the point that I let all the smoke out of the motor in the head (all electric motors have smoke in them...if you let it out, they tend to stop working).

I found another used one on our neighborhood FB page for free and have been using it, but it's a different style head and it's garbage. It's not a bump-head, it just feeds line every time you let off the trigger and get back on it. It doesn't feed reliably, it doesn't hold much line, and it's a huge PITA to reload it.

So, all of that is to say, I absolutely LOVED my 40v Kobalt and will buy another, but ONLY if it has the bump head

Isaiah 5:20