B4 paper size
Refers specifically to the B4 paper size (257 mm × 364 mm), part of the JIS B series.
This printer can print up to B4 size.
Please buy some B4 size paper.
Standard notation for B4 size paper.
Variant using the kanji 四 for 4; less common than the numeral form.
From the JIS B series paper size designation, where 'B' indicates the series and '4' the size number.