Features of tube/column radiators:
Columns:
Tube radiators consist of a series of round or oval columns that can be arranged vertically or horizontally. These columns are made of metal—typically steel or aluminum—and are available in various diameters and spacings.
Height:
The height of a tube radiator is measured from the bottom edge to the top edge of the columns. Tube radiators are available in different heights to meet the requirements of various room sizes and heating needs.
Sections:
The sections of a tube radiator refer to the number of individual columns connected together to form the radiator. To determine the number of sections, simply count the number of columns arranged vertically or horizontally.
Source: Recknagel (2020): Handbook for Heating and Air Conditioning Technology