Replacing one of this can be challenging depending on where the connection is made to the supply line. If it has easy access, it's pretty straight forward, but if it is hard to reach, the fun begins. First thing is to understand you can not remove the old bib from the outside. If you try that you will almost certainly twist the supply pipe and then you really have a mess. You must work from the inside where the connection is. Use two wrenches. One to turn the tube and the other to apply counter pressure to prevent the twisting of the supply line. When you install the new, heed the arrow on the bib to align it properly and remember there is a slight downward tilt so the bib will drain when shut off.