While one might guess that they should all fit, in a previous discussion (perhaps in another forum) I recall the discovery that there are two relatively common sizes of "lighter" or "accessory" socket. As mentioned earlier, motorcycles might be one common application of the smaller size. All of these sockets are lousy electrical connectors, used only because they were common as lighter sockets; if the whole industry started with a connector for automotive accessory power I'm sure a very different design would be chosen.
The Wikipedia page specs
suggest that the smaller size is only about half a millimetre smaller than the larger size, on average, but I have heard of the size variation causing fit problems; those specs say that the even the smallest "size B" plug won't fit into even the largest "size A socket".