Useful: Sometimes "this" just doesn't plug into "that" - When the industry standard for aftermarket lighting calls for mostly 9006 Female inputs, these adapters will come in handy. Go Direct: If your vehicle's stock headlight circuit is strong enough to power ballasts without a relay harness, these are the perfect solution for non-9006 headlight systems since almost all HID ballasts require a 9006 female input. Standard: These are standard equipment on all HD Relay harnesses which are sized for anything except for a 9006 input.