First of all, manufacturers must have complete qualifications and operating rights.
Second, it depends on whether there are excellent production technology, specialized designers, installation teams and after-sales service personnel.
Third, see if you have your own factory, so that the price will be more advantageous. Usually, manufacturers sell them at lower prices. You can also conduct on-site inspections to intuitively feel the quality of the products.

4. In fact, it is not troublesome to customize a container prefab. The key depends on how you choose. After selecting a good manufacturer, you can directly provide the drawings, or let the manufacturer design the drawings according to your own needs.
5. Sign relevant customization contracts. The relevant provisions must be noted in the contract, and the relevant details of the product, quality assurance, payment method, rights and responsibilities of Party A and Party B, delivery method, liability for breach of contract, etc.