The fixture is designed based on the principle of a reflective three-shade system, which directs the majority of the light downwards. The shades are made of mouth-blown opal three-layer glass, which is glossy on top and sandblasted matt on the underside, giving a soft and diffuse light distribution.
The PH 3½-2½ Glass Table lamp was designed in 1928 and is one of many advanced projects undertaken by Poul Henningsen in the development of his world-famous three-shade system from 1926.