They are different, and they are irrelevant. Let me tell you what A-type and B-type chains mean: there are two types of chains. One is that the standard used in A-series is ANSI, which is what we often call American standard chain, and the other is that the standard used in B-series is German standard, which is what we often call European standard chain (such as 40 chain, which is called A-series in GB standard).