According to ASTM B265 specification, Any products 0.187 inch (4.75mm) and under in thickness and 24 inch (610mm) or more in width are classified as sheet.

Range of size: 0.5 - 4.75 tk x <1000 Width x <3000 Length

Other materials like Pure Nickel, Zirconium, Niobium, Tantalum also can be provided.