You can't sell what the system doesn't know exists. Product Units: Define how you sell (Pcs, Kg, Box of 12). Variations: Use this for items like clothing (Small, Medium, Large) or electronics. Importing Products: If you have thousands of items, use the CSV import tool in S2bd Billing to save hours of manual entry. Opening Stock: When first starting, use this to tell the system what you currently have on your shelves.