"501" is just the model number.
LED bulbs are proven to use considerably less power, so much so that some cars fitted with "bulb failure" displays cannot detect properly functioning led bulbs in use and show them as failed
Another advantage over the standard filament bulb is that LED bulbs do not produce the heat that filaments can.
I've had a c5 headlight melt due to the heat caused by a filament bulb that shorted out. A new headlight from Adam is around the £40 price.
Fitting the led bulb is a money saving option in more ways than one
And yes, it is a straight forward push fit.