Hörmann blueline steel interior doors are made of double-skinned steel sheets, thickness 40 mm and lightweight but sturdy and durable at the same time. Door leaf is available for both flush and rebated structures. Standard superior multi- chambered sealings between door leaf and frame lead to high performance on both thermal and sound insulation. Blueline doors are available for various surfaces and hardware, as well as different kind of optional extras, such as glazing, top light, top panel etc., which provide more choices for customers and meet more project demands. Most of all, the high quality is ensured by industry 4.0 standardized producing process and production equipment.