Product review (5 stars): Love the water center, this filter is the key
Bought 2 of the single packs after reading someone's review that they ordered the multipack and only received a single.  Didn't want the hassle.  If anyone does successfully get the multiple, I hope they say so for my next time.

When the filter is needed, the taste of the water changes and the stream is very slow.  My refrigerator has an indicator light, but the change comes before the indicator goes on.