What plug for in seat power

Can anyone tell me what type of plug is used for the in seat power supply. I have a ' car cigarette lighter' type that I used on my last AA flight, but I have also seen on some planes the 2 pin type.
Much obliged

[HighFlyer]

Its called an 'EmPower' adapter. Its a small round plug with two pins in it, smaller than a cigarette lighter. VS do carry a number of leads onboard for common laptop types if you do not have your own.

Thanks,
Sarah

I've not tried them, but you can get converters on ebay for about £5 for 'Seat Power Adapter/Convertor to Car Lighter Female Socket 12V DC Power Supply'