Metal spring more durable and can withstand a greater load than latex. Expander is designed in such a way that it was possible to strengthen the muscles of the hand and, squeezing the handle. Thus, it is possible to train multiple muscle groups with one expanders without having to buy a separate expander to the brush. Total capacity: 50 kg. Springs removable. It is not recommended to stretch the spring of more than 1 m, as this may lead to deformation of the springs and render it unusable.