addressing preliminary comments

com.unity.ml-agents/Runtime/Communicator/GrpcExtensions.cs

                     int[] intDimensionProperties = new int[dimensionProperties.Length];
                     for (int i = 0; i < dimensionProperties.Length; i++)
                     {
-                        intDimensionProperties[i] = (int)dimensionProperties[i];
+                        observationProto.DimensionProperties.Add((int)dimensionProperties[i]);
-                    observationProto.DimensionProperties.AddRange(intDimensionProperties);
                 }
 
             }

com.unity.ml-agents/Runtime/Sensors/BufferSensor.cs

 
 namespace Unity.MLAgents.Sensors
 {
-    public class BufferSensor : ISensor
+    public class BufferSensor : ISensor, IDimensionPropertiesSensor
     {
         private int m_MaxNumObs;
         private int m_ObsSize;
             return new int[] { m_MaxNumObs, m_ObsSize };
         }
 
+        /// <inheritdoc/>
+        public DimensionProperty[] GetDimensionProperties()
+        {
+            return new DimensionProperty[]{
+                DimensionProperty.VariableSize,
+                DimensionProperty.None
+            };
+        }
+
         /// <summary>
         /// Appends an observation to the buffer. If the buffer is full (maximum number
         /// of observation is reached) the observation will be ignored. the length of
             }
             for (int i = 0; i < obs.Length; i++)
             {
-                m_ObservationBuffer[m_CurrentNumObservables * m_MaxNumObs + i] = obs[i];
+                m_ObservationBuffer[m_CurrentNumObservables * m_ObsSize + i] = obs[i];
             }
             m_CurrentNumObservables++;
         }

com.unity.ml-agents/Runtime/Sensors/BufferSensorComponent.cs

     {
         public int ObservableSize;
         public int MaxNumObservables;
+        private BufferSensor m_Sensor;
-            return new BufferSensor(ObservableSize, MaxNumObservables);
+            m_Sensor = new BufferSensor(ObservableSize, MaxNumObservables);
+            return m_Sensor;
         }
 
         /// <inheritdoc/>
+        }
+
+        /// <summary>
+        /// Appends an observation to the buffer. If the buffer is full (maximum number
+        /// of observation is reached) the observation will be ignored. the length of
+        /// the provided observation array must be equal to the observation size of
+        /// the buffer sensor.
+        /// </summary>
+        /// <param name="obs"> The float array observation</param>
+        public void AppendObservation(float[] obs)
+        {
+            m_Sensor.AppendObservation(obs);
         }
     }
 }

com.unity.ml-agents/Runtime/Sensors/IDimensionPropertiesSensor.cs

     /// The Dimension property flags of the observations
     /// </summary>
     [System.Flags]
-    internal enum DimensionProperty
+    public enum DimensionProperty
     {
         /// <summary>
         ///     No properties specified.
         /// Means that there can be a variable number of observations in this dimension.
         /// The observations are unordered.
         /// </summary>
-        VariableSize = 3,
+        VariableSize = 4,
     }
 
 
-    internal interface IDimensionPropertiesSensor : ISensor
+    public interface IDimensionPropertiesSensor : ISensor
     {
         /// <summary>
         /// Returns the array containing the properties of each dimensions of the

ml-agents-envs/mlagents_envs/base_env.py

     Means that there can be a variable number of observations in this dimension.
     The observations are unordered.
     """
-    VARIABLE_SIZE = 3
+    VARIABLE_SIZE = 4
 
 
 class ObservationSpec(NamedTuple):