A14 are more like standard case fans, they will fit where 140mm fans/radiators tend to go.
The A15 has a large frame and is really the central fan you find on Noctua NH-D15. I assume it is sold as a replacement for those. (More like a 150mm fan, but not really conforming to such a standard if it existed)
It does have mounting holes for 120mm though, so as long as you have enough room around an opening you could use this, but a standard 120mm fan would probably perform better in that situation.