An M12 fieldbus distributor is easier to order once you fix the protocol and pin map first, then the coding and contact count, and only then the housing. A cell upgrade often starts with a PLC port, a trunk cable already on the frame, and three devices that each need a drop. Two distributors can look identical at that point—same body, same nut, same contact count—while behaving differently in the panel. One may carry CAN_H and CAN_L straight through to every output; another may cross them. One may bring the shield to the shell on all ports; another may do so only on the input. Finding that out after the cable is cut costs a shift; finding it out in a drawing review before the order takes much less time.