Hi Robredo ,
im asuming you are using your 3 top 120mm fans as intake ?
if you are then why not a triple 140MM Demci flexhttp://www.demcifilter.com/p0075/Standard-Triple-140mm-Radiator-Dust-Filter.aspx
Many thanks for the reply I had a look at the link you left and found that the 140mm triple will be too large so I plan to go with the 120 mm triple as the overall size: 410mm x 150mm. Actual filter size: 380mm x 120mm which will cover up the 140 mm spaces.
I can't run triple 140s as the case only supports x2 140s and x3 120s so going with the triple 120s
Furthermore I am running the x3 120 mm fans as exhaust, the reason for the dust filter is that I am afraid that dust will get in the NZXT source 530 as it does not come with top filters and therefore not dust proof what do you think?