Hi, hoping someone can help, could anyone tell me what the part is called on the photo 

Thanks

Air Conditioning compressor.

Thank you that's great 

YW

I am more confused now, there is a hairline fracture or crack on top of this and was sure this was were my oil leak was coming from, would oil come through the air compressor 

Remove the plastic engine cover and inspect thoroughly for oil seeping from a mating surface above the A/C compressor.

Thanks Mic, will have a look and let you know