These are great for about 45-55 F. Do a good job of blocking the wind and keeping your toes warm. If you need anything warmer, you'll be in booties. They hug the shoes well, and "pop" on and off.
Their Assos, so they're expensive. But, they fit over my Sidi Shots and my Shimano cleats. Acer a dozen rides, they seem like they'll be durable as well. Kept my toes warm in temps in the mid-high 40's. I don't think they're suitable below 45F.