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. 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 New Material: Plastic+nylon+magnet Color: As Pictures Shown Normal 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