They are available for peanuts these days, and unlike most similar devices, need no batteries, which somehow - to my way of thinking makes them fit nicely with the 500 C & C/M series.
If you get one with the instructions they are very complete, considering the simplicity of use.
It is for $200 which is very much. Do you know that? Is it worth for that money?
Recently I bought Sekonic 758D. From technical point of view it is simple to operate. I seek the "tricks" how to use a h-h meter to yield the best results with my 501CM. So far, with about 30 yrs break
, I took 35 mm pictures with manual camera with TTL metering. Using such a fine instrument as Hass 501CM totally independent on batteries is a new experience for me but a very nice one.