The sizes of business cards are changing like the wind. Sizes vary by every customer, country, traditional belief or company design. Bank cards are 85x55mm, East- and Central-Europe use 90x50mm. Western-Europe mainly goes by the bank card size.
90x50mm: Great for custom designs, large color graphics and papers with diverse finishing processes (laminated, UV coated, creative sheets). Easily readable text and big designs are suitable for this size with nice projections.
85x55mm: easily stored, mainly used with rounded corners.
English spoken countries use 89x51mm due to rounding error (2×3.5in). Chinese sizes are 90x54mm, Japan compensate this to 91x55mm.
Custom sizes are used with a decreasing tendency as flyers.