For 2007, the Trets has been completely redesigned - it’s now almost a mini Kettwiesel! As with the original Trets, it will fit any child from 3’7” to 4’11” and can be towed behind any bike - what’s new is it can be quickly converted into an independent trike with it’s own brakes and steering!
It’s a fantastic combination - couple it to your bike for absolute safety on the road (with 3-point harness to keep them in place), uncouple it for independence where there’s no traffic. Or, when you don’t have company, fold the back forwards to give a large load platform for cargo.