I own quote a few Castelli items (Jackets, Vests, Short and Long Sleeve Jerseys, Gloves, and other Shoe Covers) and think they are specialist in cold weather gear. However, I was very disappointed with these shoe covers.
Visually, I noticed that there is a weird reflective strip / pull tab in the back (you can see it in the product photos). It sticks out in a weird way and is odd looking. Also, the underneath of the shoe only has very small cutouts for the cleat and back pad of the shoe. This makes it difficult to put on and off of the shoe. By contrast, my Castelli Intenso UL Shoecovers have a velcro tab closure underneath that makes it easier to put on and off and also allows additional configuration so it fits the shoes better.
I originally purchase a Large but it seemed a little loose in the store when I tried it on my shoes so I opted for a Medium so I could have a little more aero feel to them. When I went to put them on for a ride today, I realized that they appeared to fit the shoe ok (at first), but then I couldn't even get the zipper up over my calf to close it for the last inch or two. And while I have muscular legs, they are not enormous and I'm not overweight. In order to get them zipped, I had to move it down an inch or so because they do not stretch much at all.
I didn't realize until I had already ridden 6 miles or so that by moving the top of the cover down a bit, the back of the cover actually slips down underneath the shoe and doesn't hold its position. So the tiny rear opening for the back of the road shoes shifts forward so the pad of the shoe is partially covered by the shoe cove. There just isn't any way to get it to stay in position and even if I hadn't moved it down at all, I think it still would have shifted down because nothing holds it in position. But that also means that if I get off the bike at a stop light and put my foot down, the shoe cover is between my shoe and the concrete so it will wear out very quickly from constantly rubbing on the concrete.
I used them tonight on a ride in mid to low 40's with sleet and rain to start the ride. For the most part, I was still warm at first (why I'm giving them 2 stars instead of 1). But by the time the time the ride was over, my toes were frozen and my socks were soaked. So they have very sketchy dimensions, don't have adjustable closures, are hard to fit over the shoe, don't zip over my calf, and didn't even keep my feel dry or warm for a 2 1/2 hour ride. Since I've used them already, I can't return them. So they'll either just sit in my garage forever or I'll eventually just give / throw them away. They're of no use to me.
If you need a pair of shoe covers, I'd look elsewhere. Castelli does have other options that work much better that this model.
I had an older pair of Castelli shoe covers that were falling apart so I decided to give these a try, and I am glad that I did. I have worn them in weather ranging from low 40s to low 50s over my road shoes and they provide just the right amount of warmth. The Perfetto covers are extremely well made and have the best zipper I've ever used on a shoecover. I've had them for a month and can't imagine another pair doing so much so well. Love 'em!
I had previously bought other similar boots but they were not of such good quality. After using them a couple times and suffering from the cold on the road, I decided to invest a little more and be more comfortable on my rides. Now that I am more comfortable, I focus more on my performance on the bike and not on suffering from the cold on my feet.
Zippers are made of plastic and break a part ordered X large so as not to force over shoes fit properly but after four uses one zipper broke apart at base then next the other did the poorly made product do not purchasing.