The 4″ x 5″ Silhouette should be used on front flaps 12″ and 14″ wide. The 6×8″ for rear flaps all sizes. The 9×12″ can be used on 20″-24″ wide flaps if it will fit below the plastic trim. (make sure you have the length below the truck for this height).
Most orders without custom weights ship in 1-3 days