For domestic or international shipping, you must consider that the packaging you use for your shipment must be strong enough to endure the trip from you to the recipient. Individual courier parcels go through many stages of handling and need to be packed correctly. Also, sufficient tape must be used to protect the parcel from unintentional damage.
When packing a carton for your shipment, you have to consider whether it can be picked up by one person. Therefore, the carton should not exceed 30kg, especially for courier shipments.