Indeed. The speed of light is defined to be exactly 299,792,458 m/s but how much more fun it is to quote it in obscure units. I think it is around 1803 giga-furlongs/fortnight. At least a furlong is well defined (1/8 mile or approx 201m). The problem with NTUs is that they are so vague. How tall is a giraffe and what is the volume of a swimming pool? In most cases I don’t really think they help to visualise the object being described.