Can keep up running!
I started using the double when my son was 6 months and my daughter 3 years old. I used Baby Jogger Performance when I only run with one of them (have had this for 3 years). I like that I can completely recline my son and my daughter can still sit up. The visor is very large, as is the window to see the kids. It is a little more difficult managing the fixed wheel with two, but it makes for a nice smooth, fast run. Overall, a very good stroller that I would recommend to runners!