It's 304 stainless steel square ceiling shower head. Because of stainless steel material, it can be made very thin, plz refer to the detailed pics. Except the SUS304, there is ABS one.  For this series, it's SUS304 ultra thin shower head, the size can be divided into 4inch, 6 inch, 8 inch, 10 inch,12 inch, 14 inch, 16 inch, 18inch etc.