The dimensions of the Canadian series paper sizes are defined by the CAN 2-9.60M Canadian paper size standard. These canadian paper sizes are the US ANSI paper sizes rounded to the nearest 5mm. The P series includes paper sizes P1 to P6, which corresponds to the ANSI A,B,C and D, as well as two additional sizes smaller than ANSI A. The sizes now appear to be no longer used and are obsolete. The Canadian P series doesn't have a single aspect ratio like the ISO standard sizes, which makes enlarging and reducing the sizes harder. The Canadian P series are also occasionally referred to as PA1, PA2 etc.