Bought two of these one for each arm as I am suffering terribly with pain in both elbows and joining tendons after wearing them for a couple of hours found no relief whatsoever in fact the pain was worse if anything. I have tried them with and without the inserts and no difference buy a tube of voltorol gel for relief these in my opinion are useless.
If you are fed up to the back teeth with calls you do not want or ever asked for then this device is undoubtedly for you just add the numbers or area codes you want to receive calls from and you will be able to enjoy life again without someone calling about boilers, double glazing and insulation.
For the price of this book the quality of the materials used to print it on is very poor they might as well have printed it on toilet paper it is a book which is likely to be referenced many times and won't last two minutes.
It is also out of date a new version should be available to include amendment 2 released in August 2013, the amendment is available for download for a cost from the IET website so beware.