Hollow bars are essentially thick-walled seamless tubes which are manufactured via hot finishing in a bespoke tube hot-rolling mill. Such tubes offer advantages for manufacture of machine components with centrally-located holes for which starting from round bars would entail unnecessarily long processing times and excessive material losses.

Surfaces, tolerances and straightness of hollow bars are improved by cold drawing. Furthermore, cold-drawn hollow bars in a given steel are characterised by higher strength than corresponding hot-finished products.