Don't let a missing safety key stop your workouts! This replacement treadmill safety key is specifically designed for Horizon Elite treadmill models including the 2.0T, 2.1T, 2.2T, 3.0T, 3.1, 3.2T, 4.0T, 4.1T, 4.2T, 5.0T, 5.1T, and 5.2T series. The part number is 013871-A if you want to double-check compatibility with your machine. If your original key has gone missing or stopped working (it happens to the best of us), this simple replacement gets you back to running in no time. The safety key is that little magnetic clip that attaches to the console and clips to your clothing - if you fall or move too far away, it pulls out and stops the treadmill immediately. It's a crucial safety feature that shouldn't be overlooked. Installation is super simple - just plug it into the console slot and you're ready to go. Keep your workouts safe and uninterrupted with this genuine replacement part. Much cheaper than buying a whole new treadmill, right? Whether you're training for a race or just trying to stay active, this little key keeps you safe while you work up a sweat. Don't risk using your treadmill without proper safety features - this affordable fix gives you peace of mind every time you exercise.