Product review (5 stars): Fixed the Problem
Began having the water hammer problem at the refrigerator after changing the fill valve to a toilet!  The new fill valve had a much higher flow rate which caused the water pressure to drop enough that the refrigerator water line got "hammered" when the toilet valve cut off.  I used a short section of icemaker water line with compression fittings to "splice" this arrestor into the existing water line, and fashioned a bracket to mount the arrestor on the wall behind the refrigerator to hold the arrestor in an upright position.  No more water hammer problem.

Edit 9/11/2014 - The arrestor mysteriously stopped working a few days ago.  The only moving part (a small piston with a pair of O-rings keeping the water separated from the air chamber) apparently failed.  Water hammer at the icemaker returned with a vengeance.  The manufacturer says these things should last at least 50,000 cycles (a very long time).  I contacted the seller, Plumbers Outpost, thru Amazon.com to request a replacement.  The seller declined to take action citing their return policy (incorrectly as it turns out), despite saying that my arrestor probably had been defective the entire time I had it.  They told me to take it up with the manufacturer.  I then contacted Amazon.com for help.  Amazon could not compel the seller to act, and the time frame for their own A-Z guarantee had long since passed.  But that did not sit well with them, so Amazon gave me a credit for the purchase, even though this was not really an Amazon problem! This is how customer service is supposed to work, and is the main reason I have been an Amazon customer for so many years.  As for Plumbers Outpost ... I suggest you avoid them.  BTW, I fixed the water hammer problem this time with the 660-TK arrestor (sold by Amazon) that attaches to the toilet water line, since that is where the problem originated.