This quantitative filter paper has a diameter of 18cm and retains large sized particles. Our quantitative filter paper is pre-treated with double acid and washed with distilled water. It contains negligible ash content at about .01% This filter paper is recommended for precise quantitative analysis. Our filter paper is produced in circles and sized by diameter. Each pack contains 100 filters. Quantitative filters are used when you are generally concerned about what is left on the filter. Qualitative filters are used for both collecting a precipitate or solid and removing unwanted substance from your filtrate that passes through the filter, but not as concerned about he quantity of substance that remains on the filter. Sold in packs.. These are new and unused.