I know that they all have the same part number, but I remember talking to an older panel beater who said that they were handed as front right was the same as rear left as in they were diagonally opposite. When you look at them from front on the left one is slightly shorter on the left hand side as the bar joins and is double thickness on the left and single thickness bar on the right.
I thought it might be a bit "over the top" being only the extra thickness of the bar on the outer side (maybe 3mm at the most).
I have never really measured them that accurately to see if he was right or not!
Cheers Stewy