The U11 glass bulb is a dedicated dome-top sealing housing for CdS photoresistors. Fabricated from UV-cut borosilicate sealing glass, this component efficiently blocks ultraviolet light below 380nm while maintaining stable transmittance across the visible spectrum. Its thermal expansion coefficient is well-matched to Dumet wire to enable reliable hermetic sealing, protecting internal CdS chips from oxidation and performance deterioration. This glass shell is widely adopted as a standard encapsulation component for outdoor light dependent resistors.