-Customize your treatment mechanics by achieving near constant spring forces to move teeth to a more predictable end result. -These springs can be stretched 3 times their passive length to achieve desired force. -The Kit Contains: -5 springs of each strength as well as in mm length. -Comes in 9mm and 12mm in Extra Light (XL). -Light (L). -Medium (M). -Heavy (H). -Extra Heavy (XH). -50 springs in total. **For further product information, please contact Chat Support**