Shipping cost depends on more than actual weight. Air and express carriers charge by volumetric weight, calculated from package dimensions — commonly length × width × height in centimeters divided by 5000 or 6000, depending on the carrier.

This matters for drinkware in a specific way: empty stainless-steel bottles are bulky and light, so their volumetric weight is far higher than their real weight. That makes air and express freight expensive for anything beyond samples or urgent top-ups.

Sea freight is the default for bulk orders because it charges by container volume rather than per-kilogram dimensional weight. The trade-off is time — ocean transit is measured in weeks, not days.

Express couriers remain the right tool for samples, approval pieces, and small urgent restocks, where speed is worth more than the dimensional-weight premium.

Practical takeaway: Ship samples and urgent top-ups by express, but route bulk empty-bottle orders by sea to avoid volumetric-weight costs.