Ceiling hanger hooks by Convenience Concepts.  I installed a drop ceiling in my basement and these are the nicest hooks for hanging lightweight items from the ceiling.  They are made of clear plastic and are nearly invisible.  They are reusable and can easily be installed, removed and used again elsewhere.  The part of the hook that grabs the suspended ceiling bar spreads apart for installation and removal.  Very easy to install and remove.  Being made of plastic they won't scratch the finish on the grid bars.  I have 20 unopened packages with two hooks in each package.  All are new in the original sealed packages.  I used a couple of the hooks I'm using to take some of the pictures.  If you buy more than one package please wait for a combined shipping invoice.  If you do pay, no need to worry, I'll refund any overcharge for shipping that the eBay calculator charges you.