For the PA120.3...

Type "C" Self-Tapping Screws.
3.5 x 38.0 (metric - mm) / 6 x 1.5 (imperial - inches)
http://store.over-clock.com/Miscellaneous2.html#a400
4 pack of philips head self tapping screws used for fans with closed corners, which require the user to screw thru the case, thru the fan, thru neoprene gasket then into the rad...

Suitable for all ThermoChill PA Series Rads and 25mm closed-corner fans such as the Nexus 120mm... Also suitable for mounting the same fans to Performance Shroud series.
Go thru grill, thru case, thru fan, thru neoprene gasket, into rad.

grill > case > fan > gasket > rad > gasket > fan

For the opposite side of the rad (ie: the side with fans NOT against the case panel), be careful not to overtighten the screws... or you WILL puncture the core