Yesterday,after changing both my fuel filters on my Cat powered C7500,I cut open both for an inspection.I now see what makes Cat the best filter out there.The 2 micron secondary filter's metal is twice the thickness of the Racor's primary filter{ Cat does'nt make this filter} ,the paper medium is of unbelievable quality, and Cat wraps it with a hard plastic-like string in a spiral weave for added security.Nice stuff.