Features:1. Designed for protecting the runner's safety while using the treadmill. 2. Once the safety key break away from the induction area of running machine, the running machine will produce a warning tone to prevent the user from falling down and get injured. 3. Treadmill safety key: It can work easy and quick on most treadmills requiring a round treadmill safety key.4. With a strong clip:It can easily clamp to any part of your clothing and it's strong to hold.5. 3 types of running safety key, easy to fit for different diameter treadmill switch. Specification:Condition:100% Brand NewMaterial: Plastic+nylon+magnetColor: As Pictures ShownType: Large Size, Magnetic Medium Size, Magnetic Small Size(OptionalNormal type large size is suitable for diameter at the treadmill switch is greater than 32mm/1.3in.Magnetic medium size is suitable for diameter at the treadmill switch is greater than 28mm/1.1in.Magnetic small size is suitable for diameter at the treadmill switch is greater than 18mm/0.7in. Weight: Approx.24g Package list: 1 * Treadmill Safety Lock.