Even light bulbs have an energy rating, and this one is C-rated. On this light bulb you'll find a GU5.3 MR16 socket.
From Amazon
OSRAM Halogen-Reflector / DECOSTAR/ GU5.3-socket / dimmable / 12 Volt / 20 Watt / 36° beam angle / warm white - 2800K
OnBuy
OSRAM Halogen-Reflector / DECOSTAR/ GU5.3-socket / dimmable / 12 Volt / 20 Watt / 36° beam angle / warm white - 2800K