Hey treadmill owners, if you've ever lost or broken that annoying little safety key that makes your treadmill actually work, this 3-pack is an absolute lifesaver! It includes three different sizes - small, medium, and large - which pretty much covers every treadmill model out there. These are magnetic keys, which is the most common type for modern treadmills, and they work exactly like the original equipment manufacturer keys. The beauty of having this set is that you don't need to know the exact specifications of your treadmill or spend hours searching for the right replacement - one of these three sizes will almost certainly fit your machine perfectly. They're super simple to use too - just plug the right size into the safety key slot on your treadmill's console and attach the clip to your clothing, and you're ready to run. Having extras means you can keep one on your treadmill, one in your gym bag, and maybe even give one to another family member so everyone can use the machine without searching for the key. They're also great to have as backups because let's be honest, those little keys seem to disappear into another dimension sometimes. The build quality feels solid, and they function exactly like the original keys that came with your treadmill. Whether you have a NordicTrack, ProForm, Sole, Horizon, or pretty much any other brand, this set has you covered. It's one of those simple, affordable solutions that saves you from the frustration of having a perfectly good treadmill that you can't use because of a missing $2 plastic key!