I ordered TWO of these units. SM128 Profibus Gateway units from MAC. As you can see from the pictures, one unit has some extra washers under the POSTS that mount the DB-9 connector for Profibus. These washers do not allow your DB-9 connector to seat correctly. I noticed today that the second unit ordered same part number did not have the washers under the post. Before I discovered this I contacted MAC and questioned the problem. They have not responded. Not happy with the brush off I received. Poor support from MAC direct...Obviously, one of these units is wrong and one is right. Keep an EYE on this product if you order one, you can screw these together and not make a connection.