Decide the job first: lux on a surface, f-stop for a camera, or a match light in a cold shoe. Then check what the sensor can see. These listings read visible illuminance, not PPFD or UVB. Geometry is next: a fixed head, a rotating head, a split or cabled head, a sliding lumisphere, or a 45° shoe meter. Confirm the range and whether the screen shows lux, klux, or a times-ten mark. Then the kit: a case, cells in the box, and whether the written reviews are marked United Kingdom. Colour pairs here share one review text.