High-rise falls are a major urban accident for indoor cats, and a lunge at a bird can pop out a standard insect screen, which is not a guard.
Effective protection means metal or high-strength mesh, openings smaller than a cat's head can pass, and frames screwed in rather than stuck on with adhesive strips.
Add restrictors to sliding windows to cap opening width; integrated guards suit casement windows, and wide balcony rail gaps also need netting.
Inspect frames and mesh regularly for loosening and tears, and build hardware protection first before relying on the habit of checking where the cat is.
