diff --git a/Strings/XMID.Serializer.cs b/Strings/XMID.Serializer.cs
index 56605877..96e410d7 100644
--- a/Strings/XMID.Serializer.cs
+++ b/Strings/XMID.Serializer.cs
@@ -1,4 +1,4 @@
-using System;
+using System.Text;
 using SabreTools.Serialization.Interfaces;
 
 namespace SabreTools.Serialization.Strings
@@ -7,9 +7,22 @@ namespace SabreTools.Serialization.Strings
     {
         /// <inheritdoc/>
 #if NET48
-        public string Serialize(Models.Xbox.XMID obj) => throw new NotImplementedException();
+        public string Serialize(Models.Xbox.XMID obj)
 #else
-        public string? Serialize(Models.Xbox.XMID? obj) => throw new NotImplementedException();
+        public string? Serialize(Models.Xbox.XMID? obj)
 #endif
+        {
+            if (obj == null)
+                return null;
+
+            var sb = new StringBuilder();
+
+            sb.Append(obj.PublisherIdentifier);
+            sb.Append(obj.GameID);
+            sb.Append(obj.VersionNumber);
+            sb.Append(obj.RegionIdentifier);
+
+            return sb.ToString();
+        }
     }
 }
\ No newline at end of file
diff --git a/Strings/XeMID.Serializer.cs b/Strings/XeMID.Serializer.cs
index 235b5239..dc232c8a 100644
--- a/Strings/XeMID.Serializer.cs
+++ b/Strings/XeMID.Serializer.cs
@@ -1,4 +1,4 @@
-using System;
+using System.Text;
 using SabreTools.Serialization.Interfaces;
 
 namespace SabreTools.Serialization.Strings
@@ -7,9 +7,28 @@ namespace SabreTools.Serialization.Strings
     {
         /// <inheritdoc/>
 #if NET48
-        public string Serialize(Models.Xbox.XeMID obj) => throw new NotImplementedException();
+        public string Serialize(Models.Xbox.XeMID obj)
 #else
-        public string? Serialize(Models.Xbox.XeMID? obj) => throw new NotImplementedException();
+        public string? Serialize(Models.Xbox.XeMID? obj)
 #endif
+        {
+            if (obj == null)
+                return null;
+
+            var sb = new StringBuilder();
+
+            sb.Append(obj.PublisherIdentifier);
+            sb.Append(obj.PlatformIdentifier);
+            sb.Append(obj.GameID);
+            sb.Append(obj.SKU);
+            sb.Append(obj.RegionIdentifier);
+            sb.Append(obj.BaseVersion);
+            sb.Append(obj.MediaSubtypeIdentifier);
+            sb.Append(obj.DiscNumberIdentifier);
+            if (!string.IsNullOrWhiteSpace(obj.CertificationSubmissionIdentifier))
+                sb.Append(obj.CertificationSubmissionIdentifier);
+
+            return sb.ToString();
+        }
     }
 }
\ No newline at end of file