Batteria B3 near Bardonecchia is one of the few batteries in the Vallo Alpino with six guns while most had only four. It is also one of the most expensive, costing a total of 12,5 million lire with the nearby Batteria B4. For comparison a small work with two casemates could cost 150.000 lire. The six guns were installed in special casemate mountings which were only used in the two batteries.