The 85 Watt MagSafe Power Adapter features a magnetic DC connector that ensures your power cable will disconnect if it experiences undue strain and helps prevent fraying or weakening of the cables over time. In addition the magnetic DC helps guide the plug into the system for a quick and secure connection.&lt;br /&gt;&lt;br /&gt;When the connection is secure an LED located at the head of the DC connector will light up; an amber light lets you know that your portable is charging while a green light tells you that you have a full charge. An AC lead is provided with the adapter for maximum lead length while the AC wall adapter (also provided) gives users an even easier and more compact way to travel.&lt;br /&gt;&lt;br /&gt;Designed to be the perfect travelling companion the adapter has a clever design that allows the DC cable to be wound neatly around itself for easy cable storage.&lt;br /&gt;&lt;br /&gt;This power adapter recharges the lithium polymer battery while the system is off on or in sleep mode. It also powers the system if you choose to operate without a battery.&lt;br /&gt;&lt;br /&gt;Compatible with 15- or 17-inch MacBook Pro.