Selecting the correct thickness is critical for both safety and structural integrity. For frameless shower doors, a thickness of 8mm to 12mm (3/8" to 1/2") is standard to ensure stability without a metal frame. For framed doors, 5mm to 6mm is sufficient. Most importantly, ensure the glass carries the CCC (China Compulsory Certification), ANSI Z97.1 (USA), or EN 12150 (EU) marks. These certifications guarantee that the glass, if broken, will shatter into small, blunt granules rather than sharp shards, significantly reducing the risk of injury.