Upper/lower case
This is a "puzzle."  It has both upper and lower case letters!!!!!  It is lightweight; easy for kids to handle.  I chose primary colors.  Edges are smooth.  As others have commented that the "s" is hard to place because of it's shape.  I suggest placing a mark (dot or x)  on the top, front or back, which will act as a guide.  Happy with purchase.
Rating: 5 stars