Is Universal Adaptor Really Universal?

What do you mean by "M, C, D, and G adaptors"?
There is no universal naming scheme for the different types of plugs and sockets. Some sites use letters, but those letters can be different on different websites. They are usually just named after the country - French plugs, Swiss, Italian, British, US etc.; though they all have official names in the laws of that country (e.g. "BS 1363", "Schuko", ...). Yes, compilcated it is.

The best idea is to say what countries you wish and put links to photos, or see the Wikipedia article here.
The other problem is voltage. If your appliance runs on a different voltage to that coming out of the socket, you will need a voltage converter.

P.S. the reason I am being difficiult here is I have seen many times adapters advertised at airports as "European" which would not work in Switzerland or Italy.

Very few 'universal' adaptors are suitable for the UK, even if they have the correct pins mainly through lack of a fuse, amongst other things.

Heard the expression one size fits all? Ha!

Lots of good info on Amazon about adapters, I would suggest you get exactly what you need.

About a year ago I found a universal adapter, which was, on Amazon for twenty-five cents (.25) with Prime. I had to buy it despite the fact I had plenty of other adapters and accoutrements. The thing I noticed about it was its bulk. It would be easier just to buy the separate adapters you need as they take up less space. Its kind of a neat deal though, little prongs and plugs sticking out when you press the right button.

Chris, here is a website that shows the letter designation (e.g. M, C, D, & G, etc). (Note it's .EU extension. I don't know where these designations came from, but I've seen the same ones on multiple websites for over a decade, so they must have some officiality. Another website, no longer up, showed official EU designations for each one. I think the F-type is CEE 7/7 (perhaps more familiar to you, and the C-type is CEE 7/16). More important is the chart showing in which country they are used. A & B are US and most of north and central America, F is the German Schuko, used in most of Europe, E is the French variation, C is the so-called Europlug. It should be noted that the Europlug is non-grounding and rated for uses under 2½ amps, probably mostly lighting and electonic power supplies. I think the Europlug is limited to double insulated appliances.

Now that we don't need those big bulky converters anymore, carrying around those little plug adapters is quite simple, light and cheap.

Lee, I have seen lots of webpages with letter designations, but they do not have any official status. The original reference is the IEC (International Electrotechnical Commission) website, but they admit the letters are arbitrary, and they have then been copied from website to website. There is no one world authority which specifies plugs, each country has its own laws which apply to that country only. That is the problem, and that is why I was deliberately obtuse and asked the OP for pictures of what (s)he was asking about.

The two-pin Europlug (IEC type 'C') will fit in 'E' (French + many others), 'F' ('Schuko', Germany + many others), 'J' (Switzerland) or 'L' (Italy). It will not fit in 'G' (British, officially BS1363).

If it is 3-pin, most type 'E'/'F' plugs will fit in both 'E' and 'F' sockets, but not in 'J', 'L' or anything else.

Thanks for all the replies--it turns out that the web site posted by Lee is the authoritative key to figuring out which countries use each adaptor. Short answer: 'universal' adaptors are not universal, even in Europe; and definitely not for South Africa and many other global destinations.