There are a type which pulls out the outer end, and a type which reverses and rolls around to the other drum. Its torsional moment is constant and do not change depending on its strokes. Each type has standard products. Examples of application are as follows; to hang heavy stuff and carry it up and downwards light and easy; to pull and push with constant power; to press or press down with constant power all the way; to push up heavy stuff from the bottom and balance it, etc. For orders of certain quantity, we will produce with individual specification.