Mid-twenties. But it wasn't my age, so much as my resolution and the work I put into it. In my teens I didn't work towards my fluency. I went to the speech therapy session once a week. But I didn't practice every day like I was supposed to. When I went back in my 20's, I put in the work. I practiced every day. To this day I am still amazed at how quickly I was able to achieve fluency after years of *knowing* that I'd always stutter.