diff --git a/Line.Messaging/Messages/Flex/BubbleContainer.cs b/Line.Messaging/Messages/Flex/BubbleContainer.cs
index 4d9399c..40b8551 100644
--- a/Line.Messaging/Messages/Flex/BubbleContainer.cs
+++ b/Line.Messaging/Messages/Flex/BubbleContainer.cs
@@ -8,6 +8,14 @@ public class BubbleContainer : IFlexContainer
     {
         public FlexContainerType Type => FlexContainerType.Bubble;
 
+        /// <summary>
+        /// The size of the bubble.
+        /// You can specify one of the following values: nano, micro, kilo, mega, or giga.
+        /// The default value is mega.
+        /// <para>(Optional)</para>
+        /// </summary>
+        public FlexBubbleContainerSize Size => FlexBubbleContainerSize.Mega;
+
         /// <summary>
         /// Text directionality and the order of components in horizontal boxes in the container. <para>
         /// Specify one of the following values:
diff --git a/Line.Messaging/Messages/Flex/ParameterTypes/FlexBubbleContainerSize.cs b/Line.Messaging/Messages/Flex/ParameterTypes/FlexBubbleContainerSize.cs
new file mode 100644
index 0000000..efa92a0
--- /dev/null
+++ b/Line.Messaging/Messages/Flex/ParameterTypes/FlexBubbleContainerSize.cs
@@ -0,0 +1,13 @@
+
+using System;
+namespace Line.Messaging 
+{
+	public enum FlexBubbleContainerSize 
+	{
+		Nano,
+    Micro,
+    Kilo,
+    Mega,
+    Giga
+	}
+}
\ No newline at end of file