The gaskets of aluminum frames are a structural part of window and door construction (See categories for all frame gaskets).
In case of replacing the gaskets with lower quality materials (e.g., bubble gaskets, foam bubble gaskets), the behavior of the frame regarding water tightness, air permeability, and sound insulation changes completely. Additionally, no certificate is valid, and you essentially do not know the performance of what you are buying.
Fenestral uses foam gaskets which can be replaced if worn (unlike bubble gaskets). All central gaskets are made of EPDM. Solid gasket corners are used at the corners of the central EPDM gaskets to prevent any loss at the joints (a common practice is to cut the central frame gaskets at the corners of the frames at an angle and not install solid gasket corners, which can lead to potential losses from the corners). All the above are approved and tested in a test chamber by the profile manufacturer.
Below are some cross-sections:
EPDM Frame Central Gasket
EPDM Foam Gasket
Bubble Gasket
Central Gasket Corners
