HIGH-QUALITY MATERIAL.The Labor Saving Arm is made of the hardened stainless.The compression spring is made of high toughness silico-manganese steel, which is durable and elastic.Rubber handle makes the hand feel more comfortable. EASY TO USE.The height can be adjusted freely and the accuracy is controllable.Just raise the height by gripping the handle,and gently press the lock tab lower the height. JACK SPECIFICATION. Base: 3.6x3.3 inches. Height: 11.8 inches. Lifting range: 0.3-7.9 inches. Weight: 1.68 lb/pcs.The maximum lifting weight reach 530 pounds.Because our set has two pieces, we use them together, so they are stable and won't slip off easily. WIDE APPLICATION.It can be used to fix, support, squeeze and adjust various objects. Very suitable for installation in doors and windows, storage systems, ventilation systems, etc.It can increases the installation speed and reduces the stress of the installer to make them work efficiently. NOTE.The contact surface of the lifted object must be flat, because things with irregular bottom surfaces are easy to fall or slide during the lifting process.