Bellows Systems manufactures the widely known, Kopperman™ Bellows using this method. It is composed of a light gauge metal tube of one or more ply formed into a series of corrugations. Kopperman Expansion Joints can be manufactured with bellows formed from any material which has the necessary drawing quality, and the corrosion resistance required by the operating conditions of the system in which they might be installed. The standard Type 115 Non-Equalizing Expansion Joint utilizes a close-pitch single ply bellows. The standard Self-Equalizing Type 109 and Type 127 Expansion Joint utilizes an open-pitch single ply bellows. The pitch and depth of draw of any bellows can be varied and the shape modified to meet special application requirements. Multi-ply bellows are used primarily on small expansion compensators as standard equipment, and also on other large diameter Expansion Joints where significant reductions in compressive forces are desired. Extreme caution must be employed when specifying multl-ply bellows because they tend to be unstable under certain conditions. Torroidal bellows are very often used where extremely high pressure applications are encounterd.