IMPORTANT: Please note that in all the (below) videos a wrench (or spanner) is used to remove the threaded insert. We ONLY recommend using a 4mm, 5/32 inch or adjustable wrench to change a cartridge, because the faces are smooth, parallel and can be fit snugly to the flats. Pliers (Leatherman, Channel Locks, etc.) ARE NOT an acceptable tool for removing the threaded insert. This is because the jaws faces are not smooth and cannot be set squarely in parallel with the flats and thereby cause damage to the threads on the insert.