FLAT DUCT "T ITEM": A "T-piece" can be placed between the start and end points of the ventilation system, for connecting flat ducts at right angles or at right angles to each other. The rectangular cross-section ventilation ducts and the corresponding fittings make it easier to cover/hide the flexible system ki. It has a smaller "thickness" size compared to the elements of the equivalent "traditional" round cross-section pipe system, so it can also be placed in narrow places (e.g. above false ceilings, behind floor beams) without reducing (narrowing) the useful cross-section. The constrictions used in the ventilation system can result in greater pressure loss and higher noise from air flow. If the device to be installed has a connection with a circular cross-section, the so-called to one of the "transformer" adapters, which of course can also be found among the air technology accessories, within all size categories.