The green pips glow up in the dark, UV stimulated plastic, the more you expose to natural light the brighter the glow (NOT
The brightness is like the dials on a watch that glow, they are not bright, but dim, arms length away to view at maximum exposure
The switches with the green pip MUST be exposed to direct UV sunlight, if so, the exposure time can take several weeks
Note: If you have UV filtered glazed windows or not direct sunlight to the switches, then this may never be absorbed and never glow. If you put in dark place or cupboard the pip shall not be exposed.