It goes only on your front, which is where you need it if you need it. The benefit of only-onda-front is: No hot back, easier on and off, super easy to put on and take off with one hand while riding. Cheap to make and buy. Super compact and light, so it can always be with you.
It's a super useful garment that nobody else makes, you've never seen it, but I first made and used one in 1980. More than twenty years ago, by far.
I/Grant am basically a windbreakerphobe. I don't like the feeling of being in a flappy, wind-tight bubble; or the noise that comes with it.
The WINDSHIELD is flapless, thus silent.
The ones I used to use didn't have an elastic loop over the head, like this one does; or the elastics down at the bottom corners. The one around your head is useful, because let's say you want to put it on fast, and then mid-put you have to attend to something on the road. With the elastic over your head you can do that. Rearrange it in front when you have time (it takes two seconds max).
The elastics at the bottom corners allow you to tie loops and hook 'em over the brake levers, thus making a mini-poncho that won't do much for your back, but will keep the bulk of the rain off your thighs. That's not one of the boastable functions, but it was easy enough to stitch on some elastic, and you can use it as you see fit. It doesn't hurt anything.
Wind keeps it on you. If the wind isn't pressing it on you, there's no wind and you don't need it. When you climb a hill, you can either throw it over your shoulder like a Superman cape, or just off to the side, or just let it hang down off your body as you climb. It really couldn't be easier. Nothing ever gets in the way, nothing about it is challenging.
It's not the kind of thing you see out there,but is super smart, it does its job fantastically. It cuts the wind, goes on and off in two seconds, packs away to nothing, and costs little, even though it's MUSA.
Orange or red or red-orange, no choice. Coated nylon or some laminate. All water- and wind-proof, they all work the same. No reason not to have it with you if there's a chance you'll be chilly in the wind.
* simple, light, super packable
* on and off in a jiff
* embarrasses family members when worn off the bike out in public