A. The American Plumber WVC-34 are designed to work with cartridges 9 3/4" or 9 7/8" in length. The specifications may have been changed to reflect the measurements stated by the manufacturer. Many companies refer to these cartridges as 10" length even though technically they can range between 9 3/4" and 9 7/8" in length. Sometimes it depends on how the manufacturer is measuring the cartridge, from end of cartridge to end of cartridge or from the washer on the end of the cartridge to the washer on the other end of the cartridge. The WVC34 housings will also work with a wide variety of cartridge widths ranging from 2 1/8" up to 3" in diameter.