Measure before you open the range
The length of the tube has to clear the roll, including any end cap the product lists.
A postal tube is for a roll: a poster, a plan, a wrap that must not be folded. The page for Postal tubes is where Wholesale Packaging shows that line.
The published limit, if there is one
Tubes are their own range. A square carton crushes a roll or forces you to fill the corners.
A book wrap is for a flat pack. A tube is for a cylinder. They are not two sizes of the same thing.
Write the size down
Reorder the length, not a generic tube.
A Friday order on Wholesale Packaging that includes Postal tubes aims for Monday. A bank holiday on Friday or Monday moves that delivery. The 3pm cutoff is still the same-day dispatch rule.
Open Postal tubes when you already know this line. Tubes are sold as that length. Check the pack count before you treat one tube as the product. Wholesale Packaging will still dispatch an order placed by 3pm on the same day.