I had some foam cartridges for Aquaclear powerhead with( quick filter attachment )for same laying around, and cutting one in half..gave me two prefilter's for intakes.
Is coarse material with small hole in center,about eight inches long sold with quick filter attachment for the aquaclear powerheads.
Doesn't clog as quickly as the filter max prefilter material (was using),and small hole in center stretches snuggly around Ehiem,Rena,intakes.Two different cartridges for the power head = fine material ,white in color,and the black coarse foam.
White fine cartridge is for polishing water,not so good as the foam for it clog's way faster.