Black Redcord Elastic cords stiffness is 30 kg. They are excellent choice for Redcord Mini and Redcord Trainer for rehabilitation and functional training. Specially design locking mechanism is easy and safe to use. With elastic cords you can unload and ease workouts or use them to produce vibration. Vibration and labile condition makes your training more challenging. There are available two different lengths: 30 cm and 60 cm.