The swap that looks close
a deep carton is the usual substitute for postal tubes, and it is the wrong one. A book wrap is for a flat pack. A tube is for a cylinder. They are not two sizes of the same thing.
Wholesale Packaging lists Postal tubes separately because the jobs diverge as soon as the goods are on the bench.
What the right line actually does
A postal tube is for a roll: a poster, a plan, a wrap that must not be folded.
Tubes are their own range. A square carton crushes a roll or forces you to fill the corners.
If you have already mixed them
Folding a poster into a carton because the tube shelf is empty is how the job gets damaged.
At Wholesale Packaging, Postal tubes does not change the cutoff. Orders by 3pm leave the same day. Under £50 ex VAT the delivery is still available. It is just not the free threshold.
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.