Product review (4 stars): No Hammer Time - You can touch this
The mini arrester installed in just a few minutes on my toilet.  I needed only a single 5/8th wrench and that was probably overkill.  The item worked as advertised and dramatically reduced the hammer casued by the toilet.  I have a flushmate pressure assisted toilet and the valve action is extremely abrupt - leading to a very powerful hammer shock.  Couple that with the fact that my house is plumbed with PEX though that attic and walls (Florida water eats copper after enough years) and it was making one heck of a racket.  I gave it 4 stars is because the only reason I needed the mini rester was because the Sioux Chief hammer arrester I installed in the wall when I replumbed my house a decade ago had failed.  Thank Zarquan that it did not start leaking.  The beauty of this little arrester is that if it eventually fails, you can get to it and change it easily.