diff --git a/atrcopy/ataridos.py b/atrcopy/ataridos.py
index 821890e..b17f5a9 100644
--- a/atrcopy/ataridos.py
+++ b/atrcopy/ataridos.py
@@ -349,7 +349,7 @@ class AtrHeader(BaseHeader):
             raise InvalidAtrHeader
 
     def __str__(self):
-        return "%s Disk Image (size=%d (%dx%db), crc=%d flags=%d unused=%d)" % (self.file_format, self.image_size, self.max_sectors, self.sector_size, self.crc, self.flags, self.unused)
+        return "%s Disk Image (size=%d (%dx%dB), crc=%d flags=%d unused=%d)" % (self.file_format, self.image_size, self.max_sectors, self.sector_size, self.crc, self.flags, self.unused)
 
     def encode(self, raw):
         values = raw.view(dtype=self.format)[0]
@@ -409,7 +409,7 @@ class XfdHeader(AtrHeader):
     file_format = "XFD"
 
     def __str__(self):
-        return "%s Disk Image (size=%d (%dx%db)" % (self.file_format, self.image_size, self.max_sectors, self.sector_size)
+        return "%s Disk Image (size=%d (%dx%dB)" % (self.file_format, self.image_size, self.max_sectors, self.sector_size)
 
     def __len__(self):
         return 0
diff --git a/atrcopy/dos33.py b/atrcopy/dos33.py
index 6282536..f2c228e 100644
--- a/atrcopy/dos33.py
+++ b/atrcopy/dos33.py
@@ -361,7 +361,7 @@ class Dos33Header(BaseHeader):
         BaseHeader.__init__(self, 256)
 
     def __str__(self):
-        return "%s Disk Image (size=%d (%dx%db)" % (self.file_format, self.image_size, self.max_sectors, self.sector_size)
+        return "%s Disk Image (size=%d (%dx%dB)" % (self.file_format, self.image_size, self.max_sectors, self.sector_size)
 
     def check_size(self, size):
         if size != 143360: