They are great. Unlike some other plastics I've bought at Autozone that didn't stay in place well, these work well. I use a rubber mallet to pound them in place. They are tall and wide. The curve fits. They're mostly rubber and that rubber contact on the bottom seems to help them stay in place too. They're expensive and the delivery time isn't fast, but this is the best example of a wheel chock I've seen. I use it to lock the wheels on ATVs and vintage tractors when moving them on a trailer. You will not be disappointed.