diff --git a/docs/level-response.rst b/docs/level-response.rst
index 71492ae..f47a32b 100644
--- a/docs/level-response.rst
+++ b/docs/level-response.rst
@@ -2687,6 +2687,10 @@
 
 					type:`string <appendices.html#glossary-string>`_
 
+   .. container:: description
+
+      The symmetry code. Designates how the factors will be specified. NONE: No Symmetry - all Coefficients are specified, corresponds to A in SEED. ODD: Odd number Coefficients with symmetry, B in SEED. EVEN: Even number Coefficients with symmetry. C in SEED.
+
 
 :raw-latex:`\noindent\rule{\textwidth}{1pt}`
 
diff --git a/fdsn-station.xsd b/fdsn-station.xsd
index e4bc65b..826fbfc 100644
--- a/fdsn-station.xsd
+++ b/fdsn-station.xsd
@@ -798,6 +798,14 @@
 			<xs:extension base="fsx:BaseFilterType">
 				<xs:sequence>
 					<xs:element name="Symmetry">
+        		<xs:annotation>
+        			<xs:documentation>
+                The symmetry code. Designates how the factors will be specified.
+                NONE: No Symmetry - all Coefficients are specified, corresponds to A in SEED.
+                ODD: Odd number Coefficients with symmetry, B in SEED.
+                EVEN: Even number Coefficients with symmetry. C in SEED.
+              </xs:documentation>
+        		</xs:annotation>
 						<xs:simpleType>
 							<xs:restriction base="xs:NMTOKEN">
 								<xs:enumeration value="NONE"/>