diff --git a/boxes/__init__.py b/boxes/__init__.py
index 2f729c9..b106622 100755
--- a/boxes/__init__.py
+++ b/boxes/__init__.py
@@ -278,7 +278,7 @@ class Boxes:
                         "Default Settings")
         defaultgroup.add_argument(
             "--thickness", action="store", type=float, default=3.0,
-            help="thickness of the material [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#thickness)")
+            help="thickness of the material (in mm) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#thickness)")
         defaultgroup.add_argument(
             "--output", action="store", type=str, default="box.svg",
             help="name of resulting file")
@@ -288,7 +288,7 @@ class Boxes:
             help="format of resulting file [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#format)")
         defaultgroup.add_argument(
             "--tabs", action="store", type=float, default=0.0,
-            help="width of tabs holding the parts in place in mm (not supported everywhere) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#tabs)")
+            help="width of tabs holding the parts in place (in mm)(not supported everywhere) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#tabs)")
         defaultgroup.add_argument(
             "--debug", action="store", type=boolarg, default=False,
             help="print surrounding boxes for some structures [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#debug)")
@@ -297,10 +297,10 @@ class Boxes:
             help="label the parts (where available)")
         defaultgroup.add_argument(
             "--reference", action="store", type=float, default=100,
-            help="print reference rectangle with given length (zero to disable) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#reference)")
+            help="print reference rectangle with given length (in mm)(zero to disable) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#reference)")
         defaultgroup.add_argument(
             "--burn", action="store", type=float, default=0.1,
-            help='burn correction in mm (bigger values for tighter fit) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#burn)')
+            help='burn correction (in mm)(bigger values for tighter fit) [\U0001F6C8](https://florianfesti.github.io/boxes/html/usermanual.html#burn)')
 
     @contextmanager
     def saved_context(self):