They perform well but are very difficult to get on the shoe. I wear a pair of Shimano road shoes (size 45) and purchased these in LargeXL, these are a very tight fit, actually pinch my fingers trying to pull them on the shoes.
I had been using one of two options - 1) a full neoprene shoe cover or 2) a Belgian bootie. I found the neoprene to be overkill on most rides because, as a rule, the temps and wind chill in my area don't require it. However, the Belgian bootie was not sufficient to keep the toes warm on cooler and windier rides. The PI Elite Thermal toe covers fit right in the sweet spot and are easy to remove and roll up in a tiny little bundle to store in a jersey pocket if needed.
These are awesome. I was a skeptic, they're so short how could they actually keep your feet warm? Then I borrowed my husband's and then I hid them so I could wear them again because they're really awesome. Then I got wise and bought my own pair. Perfect when it's not too soggy out but you need some extra toe insulation. Not suitable for full on rain and puddles though.
I use these for my commute to work when the weather is cool but relatively dry. They really keep the Columbia River Gorge winds off my toes. I use mountain biking shoes which are bigger than equivalent bike shoes, and the covers are really tight. That is the only complaint.
I wear a size 46 Euro and the LargeXLarge Toe Cover size is too small. I already ripped the lining that goes just past the cleat by stretching it too much when putting them on. I would definitely purchase this product again but not unless I get a pair at least one size, if not two sizes larger. Who sells such larger sizes will likely be hard to find. They do a good job to keep your feet warm down to about 50 degrees, below that they may help minimally but your feet will still get chilled, especially if on the bike for more than an hour in temps in the 40s wearing one pair of socks as I do. It looks like my pair will not last beyond this Winter but at least now I know the sizing.
When I first put them on I didn't notice a difference in how warm my toes were but as the day heated up and I took them off, it was incredible noticeable how these toe covers blocked the wind and held in heat. I don't leave on morning rides anymore without them!
For the price, these shoe covers are tough to beat. The larger size fit my size 43.5 shoe nicely with Shimano SPD-SL cleats. Kept my feet warm on some chilly rides up and down Mt Diablo in Northern California.