As Charles started into... Fleece has more depth than paper. When new, it will initially pass through a bit of particles, then as it is used and gets particles into the depth of the fibers, it will work better and better... until it is full, then it will be restrcited.
Overall, the longterm filtration ratings are usually better for fiber filtration. But that depends who tested the ratings and how they tested it. Rarely does someone test partially dirty filters, because they don't realize that dirty filters have better filtration rates.
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"Usually learning skills and tooling involves a progression of logical steps."