ASUS 45W 20V Laptop Charger Adapter with 4.0mm Pin Compatible for Asus VivoBook X540 X412 and M509 Models. ASUS notebook power adapters keep you going and charged wherever and whenever needed. Keep notebook batteries topped up via any compatible power outlet, or even work continuously without the battery. With an extra adapter, you can leave one at home and bring another to the office for an easier and less cluttered commute. Additional power adapters for your notebook mean you’re always prepared and charged, whether at home, the office, or on the road.