Flexible adaptors appear in many socket sets / screwdriver sets and
they're almost all the same except the 'Snake' driver. Your money would be
better spent on a decent screwdriver set containing a flexible adaptor
such as this: http://lamats.co.uk/acatalog/JCB_60pc_Screwdrivers.html
Those I have are not particularly flexible and as others have said they
don't provide much torque (tightening power).
We sell the JCB range of tools at work and IMHO they're chocolate.
Tom