I can't find a picture, but I think Patty means this:
You know how some ballet flats, instead of being completely flat on the bottom have a little like 1/4" or less lift on heel portion of the sole?
Sometimes it is the shape of a chunky block heel (i.e. the shape of the whole back 1/3 of the sole, just about an 1/8" thick).
Other times, it seems like there is just a piece of rubber or leather "stuck" onto the sole. A lot of times it doesn't cover the whole "heel" portion of the sole, but is shaped like a 2-D tear (like a pear-shaped diamond outline). The rounded bottom area of the "drop" is set back a little way from the back edge of the sole, and then the "drop" comes to a point near the arch.
Sometimes they are kinda oval shaped instead.
However, I think the main concern is that they don't seem particularly firmly attached to the soles of flats. Usually you don't see any stitching, and flats tend to have cheap- soles to begin with.
I think Patty was asking if anyone has had problems with the (apparently glued on?) extra "heel" piece popping off, peeling away from the shoes, or otherwise impacting comfort, function, or wear?