New replacement LED Downlights directly replace existing downlights.
At just 5W each they are 8 times more efficient than Halogen bulbs.
There was a time when it was more cost effective to replace the halogen bulb for an LED bulb and re-use the existing fitting. Now it is believed more reliable and just as cost effective to replace the whole light unit. New LED downlights fit directly into the whole of the Halogen lights they replace and are available with a range of options.