This 3-Up Necking Machines reduce the outside diameter of thermoplastic tubes. Tubing is heated to a temperature at which the yield strength of material is substantially reduced. The dimensional change is then accomplished by stretching the material in an axial direction. Common applications include: catheter shaft neck-down, heat shrink tubing sizing, polymer tubing layering and tubing jacketing (e.g. jacketing S.S. hypotube shafts or wire braids with polymer tubing).