Isofix or not

Mercedes handbook says isofix child restraint system in situ ,but all the searching around the gap between rear seat back and base just reveals two small vertical tube affairs about 1 inch tall either side of central section of rear seat back about 12 inches apart which look nothing like the horizontal staple shape affairs described and pictured in the handbook, the handbook says restraints are also located by the outer sides of the seats, again on either side ,no sign of these at all, anyone know are these two vertical tube affairs for child seat attachments or is the adult seat belt securing a child seat the only option, all seems a bit sketchy to me and haven't really got the time to fap around at a Mercedes dealers as the cars in use every day by my missus, minus the grandson. anyone Know the answer,Thanks