How to remove bottom fan on cooler master box 5 lite rgb

[lukehos.lions]

I just bought a new case and wanted to swap out the default fans for some better ones I also bought
However the bottom fan has a different mount, and I can't work out how to remove it.

 

[Barty1884]

Can you post a pic of the issue/mount?

Can't find many reviews that mention the fans specifically..... and in images, they appear to be the same fan, so should use the same mount (in theory).