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 1Designed for protecting the runner's safety while using the treadmill. 2Once 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. 3Treadmill safety key: It can work easy and quick on most treadmills requiring a round treadmill safety key. 4With a strong clip:It can easily clamp to any part of your clothing and it's strong to hold. 53 types of running safety key, easy to fit for different diameter treadmill switch.