The 85W MagSafe 2 Power Adapter features a magnetic DC connector so if someone should trip over it, the cord disconnects harmlessly and your MacBook Pro stays put safely. It also 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. 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. Compatible with MacBook Pro with Retina display.