diff --git a/CHANGELOG.md b/CHANGELOG.md
index a3f149df..b704582d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,7 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 
 ### Added
 
-- Nothing.
+- Provided a Size Helper class to validate size values (pt, px, em)
 
 ### Changed
 
diff --git a/src/PhpSpreadsheet/Comment.php b/src/PhpSpreadsheet/Comment.php
index e2fcd83e..7aaf9759 100644
--- a/src/PhpSpreadsheet/Comment.php
+++ b/src/PhpSpreadsheet/Comment.php
@@ -129,13 +129,13 @@ class Comment implements IComparable
     }
 
     /**
-     * Set comment width (CSS style, i.e. XXpx or YYpt).
+     * Set comment width (CSS style, i.e. XXpx or YYpt). Default unit is pt.
      */
     public function setWidth(string $width): self
     {
-        $result = new Size($width);
-        if ($result->valid()) {
-            $this->width = $result->size() . $result->unit();
+        $width = new Size($width);
+        if ($width->valid()) {
+            $this->width = (string) $width;
         }
 
         return $this;
@@ -150,13 +150,13 @@ class Comment implements IComparable
     }
 
     /**
-     * Set comment height (CSS style, i.e. XXpx or YYpt).
+     * Set comment height (CSS style, i.e. XXpx or YYpt). Default unit is pt.
      */
     public function setHeight(string $height): self
     {
-        $result = new Size($height);
-        if ($result->valid()) {
-            $this->height = $result->size() . $result->unit();
+        $height = new Size($height);
+        if ($height->valid()) {
+            $this->height = (string) $height;
         }
 
         return $this;
@@ -171,13 +171,13 @@ class Comment implements IComparable
     }
 
     /**
-     * Set left margin (CSS style, i.e. XXpx or YYpt).
+     * Set left margin (CSS style, i.e. XXpx or YYpt). Default unit is pt.
      */
     public function setMarginLeft(string $margin): self
     {
-        $result = new Size($margin);
-        if ($result->valid()) {
-            $this->marginLeft = $result->size() . $result->unit();
+        $margin = new Size($margin);
+        if ($margin->valid()) {
+            $this->marginLeft = (string) $margin;
         }
 
         return $this;
@@ -192,13 +192,13 @@ class Comment implements IComparable
     }
 
     /**
-     * Set top margin (CSS style, i.e. XXpx or YYpt).
+     * Set top margin (CSS style, i.e. XXpx or YYpt). Default unit is pt.
      */
     public function setMarginTop(string $margin): self
     {
-        $result = new Size($margin);
-        if ($result->valid()) {
-            $this->marginTop = $result->size() . $result->unit();
+        $margin = new Size($margin);
+        if ($margin->valid()) {
+            $this->marginTop = (string) $margin;
         }
 
         return $this;
diff --git a/src/PhpSpreadsheet/Helper/Size.php b/src/PhpSpreadsheet/Helper/Size.php
index 27d5e62c..12bccaad 100644
--- a/src/PhpSpreadsheet/Helper/Size.php
+++ b/src/PhpSpreadsheet/Helper/Size.php
@@ -35,4 +35,9 @@ class Size
     {
         return $this->unit;
     }
+
+    public function __toString()
+    {
+        return $this->size . $this->unit;
+    }
 }