Instruct: Classify the given Amazon review into positive or negative sentiment.
Query: Micron rating of filter cartridge

I noticed that the Brita cartridges did not take out a lot of color from the water I put in. Later I found out that it was rated Class 5 on NSF's scale - by looking up the NSF site, Class 5 means 85% reduction of particles between 30 to 50 microns. The scale is a 6-step scale with Class 1 being the best. After checking with the Greater Vancouver Water District, our sediment particle size in the water averages 2.5 microns - No wonder the water coming through the cartridges is still yellowish brown in color!