To do this activity you need a bag with matching geometric pairs. I have a bin of wooden items that I ordered from Casey's Wood Supply, and they seemed perfect for this activity. The child wears a blindfold and uses her sense of touch to find matching objects.
I introduced the stergonostic bag to O on Sunday afternoon. She seemed to enjoy it and did fairly well. On Monday, she had more difficulty and didn't want to wear the blindfold.