I guess I should research a little before looking stupid here.

"MP2 Harborlite media is the preferred choice where a High Purity, direct replacement is needed for Food Grade Harborlite perlite filter aid. Other than the addition of an acid washing purification step, the MP2 Harborlite perlite manufacturing process is similar to that of conventional Harborlite perlite filter aid. This similarity produces a media that will minimize differences in filtration processes." Taken from a site that makes the stuff. It's greek to me but we are for sure talking filtration here.

Later, Dennis