These heavy duty 4mm gold plated connectors are a must for high power electric models. Thanks to their ingenious design the positive connector has an initial low current section so that when you first plug them half way in there is no spark. Once you press two small tabs then the connector can be fully connected allowing full current. This system helps to reduce the risk of a sudden power surge damaging your ESC when you first plug in. The design also provides no chance of incorrect polarity connection.
Once soldered up there are plastic guards that clip on each connector giving you a neatly wired plug and helps to prevent short circuits.