there use to be 3 kinds of fans. ones for case, ones for rads and ones that do both. but one of them is gone. so now you got case fans or rad fans. but some only make a mix.
then your throw the rgb in to it and now there like many different kinds of rgb fans...
thrmalright is just at this time making everything and coming in a good price to Canadians witch is nice to see.
oh there also barrings but most dont care about it. and revers fans
guess there different sizes, thicknesses, speeds too