Wafer shipping box and a lower retaining member thereof

A wafer shipping box comprising:

• a case including a base, a cover detachably connected to said base, and a receiving space defined by said base and said cover;
• and
• a positioning unit disposed in said receiving space, and including a lower retaining member that is connected to said base, an upper retaining member that is connected to said cover, and a cassette that is disposed between said upper and lower retaining members,
• wherein said cassette includes two upright holding walls that are spaced apart in a left-right direction and opposite to each other, each of said holding walls having a plurality of lateral confining slots aligned in a front-rear direction, each of said lateral confining slots extending in a top-down direction and having a top end opening and a bottom end opening, said upper retaining member being formed with a plurality of upper confining slots that respectively correspond in position to said lateral confining slots of said holding walls, said lower retaining member being formed with a plurality of lower confining slots that respectively correspond in position to said lateral confining slots of said holding walls, each of said lower confining slots being defined by two slot walls that are interconnected at bottom ends thereof to form a slot bottom, and that have upper ends spaced apart from each other, said slot bottoms of said lower confining slots being respectively misaligned from central positions of said lateral confining slots of said holding walls along the front-rear direction.