Wiper blades aren’t identical because car windshields differ from each other. Some are wider, others are taller. The geometry of wipers motion along the windshield isn’t the same either. Some move in parallel, some not. Besides, for some cars, one wiper can be longer than another. Taking the incorrect wiper size might result in worse operation. The blades might hit each other or a windshield rim, not stick appropriately or leave important spots on the glass untreated. To find a correct wiper size for your car, consult your vehicle manual or simply check the online charts widely available.