Yes, there can be size restrictions on the quantity of items that can be transported through on board courier services in China. Each courier service provider may have its own limitations on the size and weight of the items that can be transported at once. These restrictions are in place to ensure that the items can be safely transported and to comply with transportation regulations.
It is advisable to check with the specific courier service provider in China for their size and weight restrictions before sending your items. They will be able to provide you with detailed information regarding the quantity and size limitations based on their policies and capabilities.