Hopefully that's unfolded, I really don't see 23 x 40 x 4 being a legal carry on on any airline. Thats significantly above the 45 linear inches United allows (that's like 67 inches).
Carry-on bag dimensions should not be more than 9" x 14" x 22" (length + width + height) or 45 linear inches (the length, height and width added together).