The profile thickness and the steel core together guarantee form stability and longevity. And: all PREMIO windows, even smaller forms, have a steel core reaching far into the window's corners (which cannot be taken for granted in other windows). Furthermore, the corner bearings and fittings are always screwed right into the steel core.

The steel core is always designed long enough to reach sufficiently far below the corner bearing and shear bearing to ensure two screws can be anchored inside it. This is very important for steadily moving the window casement and safely operating it, even after many years. This is also ensured by a casement lifting feature.

It prevents the permanent strain of the upper outer corner bearings, which would otherwise bear the total weight of the window: when closing the window casements, it will automatically be guided into the correct position in the center of the window (i.e. the window is prevented from sagging at the handle side) and supported. The wider the window casement, the more important!