4x MR16 (GU5.3) to GU10 Light Bulb Adaptor. Consult an electrician if unsure. That is to say you can not simply put this adaptor into a 12V MR16 socket and then expect a 220-240V GU10 bulb to work. This adapter allows you to use a GU10 Light Bulb in a MR16, GU5.3 Lamp Socket.
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