diff --git a/SabreTools.Models/CHD/Constants.cs b/SabreTools.Models/CHD/Constants.cs
new file mode 100644
index 0000000..46ad7a1
--- /dev/null
+++ b/SabreTools.Models/CHD/Constants.cs
@@ -0,0 +1,17 @@
+namespace SabreTools.Models.CHD
+{
+    public static class Constants
+    {
+        public const string SignatureString = "MComprHD";
+
+        #region Header Sizes
+
+        public const int HeaderV1Size = 76;
+        public const int HeaderV2Size = 80;
+        public const int HeaderV3Size = 120;
+        public const int HeaderV4Size = 108;
+        public const int HeaderV5Size = 124;
+
+        #endregion
+    }
+}
\ No newline at end of file