The type of finning normally used is a wavy base. The tape is wrapped around the tube, after pre-corrugation, with stretching to the limit of elasticity and welded with an appropriate procedure. This, in addition to offering good production economy, ensures excellent heat transmission between the inner tube and the fin, guaranteeing a high global exchange coefficient. The materials of the tube and fins can be combined according to the needs of the customer and of the operating conditions. It is also possible to produce tubes with transversal fins welded continuously (indicated for the transmission of heat by radiation).