-B
Specifies the default file buffer size in bytes.
Syntax
-BsizeThere is no space between -B and the size value.
                  
If size is not specified, then the default size is 1MB, which
                                                  is your C library default file buffer size
                                                  (BUFSIZ). The minimum value is
                                                  16KB and the max is 4MB.
                  
Example
-B16384