Thanks for getting back to us, Campbell.
When importing inventory items in QuickBooks Desktop (QBDT), you're allowed to enter 31 characters for the Item name and part number. Then 4095 characters for the Description (Invoices).
You can check out this link to learn more about character limits in QBDT: Character limitations for fields in QuickBooks.
Once your client is ready to import their inventory item, you can share with them this article that can guide them through the process: Import and export data in QuickBooks Desktop.
I'm also adding this resource that you can share with your clients in case they need to edit and delete their items: Add, edit, and delete items.
Let me know if there's anything else I can assist you with about importing inventories in QBDT. I'm always here ready to back you up anytime.