Currently there are two configurations of conventional 6 pin XLRs. The NEUTRIK 6 pin XLR meets the industry standard according IEC 61076-2-103. Nevertheless NEUTRIK offers both types of 6 pin configurations. The standard NEUTRIK 6 pin has black insert - the insert of the non-standard configuration is gray.

The difference in the part #s is the addition of an “S” – for example:
Standard 6 pin male XLR cable connector –nickel housing/silver contacts = NC6MX
Same part with non-standard pin configuration = NC6MXS