get from car audio shop, after doing up cars, they may have looser smaller pieces to sell cheep cheep.

also, some fans run differently facing up or facing down. eg; slower when facing down ( airflow down ), faster when facing up ( airflow up ).

good bearing fans have little resistance while sleeve bearing fan or lower grade ball bearing fans are usually like this & they have shorter life span.

if ur curious to know how good ur fan is, try holding ur fan while its running & flip it around 360degree - any how flip, and u may notice at some angles, there is more vibration & the rpm drop. U can monitor this by plugging it into ur mobo 3pin header ( for rpm sensor able fan ) and monitor the fan speed.

quite fun to understand your fans' characteristics like that. then u can plan where & how to put them.

hf man..