Besides, we have waterproof paper at the bottom of each case to avoid rain and humidity.
每个箱子底下都有防水纸张，以免货物被潮湿和雨水侵蚀。
英语百科
Waterproof paper
Waterproof paper is good for extreme outdoor, marine, field use and general wet environments. Often designed especially for printing topographic maps. It is normally durable and tear-resistant.
The paper is created with special coatings and fibers to allow it to stay together and not change shape or texture when exposed to rain, dampness, or immersed in water.