26 mm Beryllium Dome Tweeter4 ohm, Neo Magnet, Small Chamber, Grill- 1" Beryllium Diaphragm (99% pure Be)- High Power Patented SD-2 magnet system- Die Cast Housing & Face Plate- Large Roll Surround f. wide dispersion- Compact Non Resonant Alu Rear Champer- Sound Transparant Protective Grill LINK: Beryllium Safety Data Sheet