Product Dimensions

Shipping Rates are calculated based on weight only.
As is the case for Hongkong Post.

To clarify a bit, HK Post has certain dimensional limitations for each type of package and parcel.

As long as you’re within those limits, the rate is calculated based on weight only.

One exception is the new Vantage service, which does use volume-weight calculations.

https://hongkongpost.hk/en/sending_mail/international/vantage/index.html

Cheers