The dimensions of a twin flat sheet can vary depending on the specific manufacturer or country. However, a common standard size for a twin flat sheet is approximately 66 inches (167.64 cm) wide and 96 inches (243.84 cm) long.
It's worth noting that these measurements are approximate and may vary slightly between different brands or regions. It's always a good idea to check the specific measurements provided by the manufacturer or retailer when purchasing a twin flat sheet.