Product review (4 stars): Manufacturer defect, but they are replacing the defect
I purchased these filters primarily because they protect against lead (as well as the other standard odor and tastes).  When they arrived I took the first filter out and it would fit.  I re-read all of the instructions and tried several more times, to no avail.  I decided to switch the filter for another one and I was able to get the filter to install.  Upon comparing the defective filter and the one that fit, I noticed that the markings/knobs on the base of the filter did not match up exactly to the ones where the filter that fit did. I called the phone number for the company on the instructions paperwork that came with the filters and they replied immediately.  The customer service rep was very polite and professional.  She asked me a couple details and I then had an email to reply back to her with photo evidence of the issues as well as provide my phone # and address so they could replace my defective filter.  They have stayed in touch with me every bit of the way and I will be buying more filters from them in the future.