these are perfect prefilters.
Not too coarse, nor too fine.
The sponge holds up to repeated cleanings.
I clean mine every 2 weeks and they save lits of food and gravel from ending up in my filter.
I run these on every canister and HOB I own.
Only negative is the plastic adapters are VERY fragile.
BE VERY GENTLE WITH THEM, THEY USUALLY CRACK, BUT ARE STILL USUABLE.
Manufacturer needs to fix this plastic, otherwise prefect.