Product review (5 stars): if you have any sensitive items like refrigerator ice machines
My LG washer (love it) made the pipes bang and shake.  I had no idea it was a known condition called "Water Hammer".  Anyways, threw a couple of these puppies on the hose fittings in the back (Well, not this exact one, but the one with the hose fittings), and BOOM!  No more banging.  Also, if you have any sensitive items like refrigerator ice machines, these arresters are recommended so that the water hammer the washing machine is creating does not bang the insides of your expensive ice machine.