The 157/1P (1571P) backbox is the standard Australian and USA back box size and shape in plastic for internal walls. It is used for all the rectangular switches in the C-Bus ranges including the eDLT but not for the Reflection range of input switches.
It can be placed vertically for the Saturn and Neo ranges and horizontally for the Modena range.
eDLT
Saturn Zen
Saturn
Modena