They actually work!
I desperately need height on the top of my head.  These clips actually do provide lift.  I don't know how well they would work on straight hair.  I always end up with an indention near the root where I clip these.  That doesn't matter that much on my hair because it's curly and the waves it creates works with curls.  I use my blow dryer with these in to speed up the drying process.  The air does flow through somewhat.  But these things are painful!  I haven't figured out how to use them without them pulling.  If I put them close to my scalp, they pull.  If I put them down a little, they pull.  I usually just dry them as quickly as possible and take them out.  They do work.
Rating: 4 stars