The sail is worlds better than a conventional umbrella, as you can a lot easier to move it spontaneously. And this is actually constantly needed, unless you're running stubbornly straight. Perfect however, it is not, but that's probably not possible. For example, my daughter (8 months) begins to complain about when it no longer sees me - which is the case when I fully open the sail. And also the lateral displacement can not be so easily transpose because the cords are no longer properly tensioned. But is perhaps the stroller (Mutsy) or to me. Nevertheless, the sail is preferable to any screen.
