Adjustable length, easy to disassemble special manufacturing spring, strong rebound force. 3. Breathable non-slip fabric with venting holes; suitable for climbing stairs, climbing, sports, etc. Specifications: Color: black Material:Belt+Alloy Type:Single bubble bag / pair color box Body material: polyester fiber Color box packaging size: 31*10*9cm Package Included: 1 Pair * Knee Booster Notes: 1. Due to the difference between different monitors, the picture may not reflect the actual color of the item. We guarantee the style is the same as shown in the pictures. 2. Due to different personal measuring techniques, there might be 1-3cm error of the physical. Thank you!