Worked fine for what we used them for. I wish they were just slightly thinner - as is, if you just stick these to the bottom of the block of wood, you're just pushing the clearance limits for the BSA pinewood derby. We got through ok, but a stricter person might have failed it. And you want these on the very bottom, to keep center of gravity low. But overall, this is a very convenient way to add weight as opposed to giant lead pieces or other setups. It only takes a few seconds to install, and allows you to fine-tune the weight to get at the exact limit.