Height isn’t the only drama queen here. A standard sliding door is usually 5, 6, or 8 feet wide. That’s the total width of the frame, but the opening is only half of that—because physics hates you and requires one panel to slide behind the other.
So if you buy a 6-foot wide door, you get about a 3-foot wide passage. That’s just enough for a human, a pizza box, and a cat, but not all three at once.