diff --git a/src/berack96/sim/util/graph/Graph.java b/src/berack96/sim/util/graph/Graph.java
index 6b88e23..44e2747 100644
--- a/src/berack96/sim/util/graph/Graph.java
+++ b/src/berack96/sim/util/graph/Graph.java
@@ -116,7 +116,7 @@ public interface Graph<V, W extends Number> extends Iterable<V> {
      * @throws NullPointerException     if one of the param is null
      * @throws IllegalArgumentException if the vertex is not contained in the graph
      */
-    void mark(V vertex, String mark) throws NullPointerException, IllegalArgumentException;
+    void mark(V vertex, Object mark) throws NullPointerException, IllegalArgumentException;
 
     /**
      * Remove the selected mark from the vertex.<br>
@@ -126,7 +126,7 @@ public interface Graph<V, W extends Number> extends Iterable<V> {
      * @throws NullPointerException     if a param is null
      * @throws IllegalArgumentException if the vertex is not contained in the graph
      */
-    void unMark(V vertex, String mark) throws NullPointerException, IllegalArgumentException;
+    void unMark(V vertex, Object mark) throws NullPointerException, IllegalArgumentException;
 
     /**
      * Unmark the vertex selected.<br>
@@ -148,7 +148,7 @@ public interface Graph<V, W extends Number> extends Iterable<V> {
      * @throws NullPointerException     if the vertex is null
      * @throws IllegalArgumentException if the vertex is not contained in the graph
      */
-    Collection<String> getMarks(V vertex) throws NullPointerException, IllegalArgumentException;
+    Collection<Object> getMarks(V vertex) throws NullPointerException, IllegalArgumentException;
 
     /**
      * Remove the selected mark from all the vertices
@@ -156,7 +156,7 @@ public interface Graph<V, W extends Number> extends Iterable<V> {
      * @param mark the mark to remove
      * @throws NullPointerException if the mark is null
      */
-    void unMarkAll(String mark) throws NullPointerException;
+    void unMarkAll(Object mark) throws NullPointerException;
 
     /**
      * Remove all the marker to all the vertex.<br>
@@ -488,7 +488,7 @@ public interface Graph<V, W extends Number> extends Iterable<V> {
      * @param marker the marker
      * @return a sub-graph of the current graph
      */
-    Graph<V, W> subGraph(String marker);
+    Graph<V, W> subGraph(Object marker);
 
     /**
      * Get the minimum path from the source vertex to the destination vertex.<br>
diff --git a/src/berack96/sim/util/graph/MapGraph.java b/src/berack96/sim/util/graph/MapGraph.java
index 451eeb9..d13b04d 100644
--- a/src/berack96/sim/util/graph/MapGraph.java
+++ b/src/berack96/sim/util/graph/MapGraph.java
@@ -32,7 +32,7 @@ public class MapGraph<V, W extends Number> implements Graph<V, W> {
     /**
      * Map that contains the vertex as key and all the marker as the value associated with that vertex.
      */
-    private final Map<V, Set<String>> marked = new HashMap<>();
+    private final Map<V, Set<Object>> marked = new HashMap<>();
 
     /**
      * Need this variable for not calculating each time the SCC or the cyclic part if the graph doesn't change
@@ -103,16 +103,16 @@ public class MapGraph<V, W extends Number> implements Graph<V, W> {
     }
 
     @Override
-    public void mark(V vertex, String mark) throws NullPointerException, IllegalArgumentException {
+    public void mark(V vertex, Object mark) throws NullPointerException, IllegalArgumentException {
         checkNullAndExist(vertex);
         checkNull(mark);
 
-        Set<String> set = marked.computeIfAbsent(vertex, (m) -> new HashSet<>());
+        Set<Object> set = marked.computeIfAbsent(vertex, (m) -> new HashSet<>());
         set.add(mark);
     }
 
     @Override
-    public void unMark(V vertex, String mark) throws NullPointerException, IllegalArgumentException {
+    public void unMark(V vertex, Object mark) throws NullPointerException, IllegalArgumentException {
         checkNullAndExist(vertex);
         checkNull(mark);
         marked.get(vertex).remove(mark);
@@ -125,13 +125,13 @@ public class MapGraph<V, W extends Number> implements Graph<V, W> {
     }
 
     @Override
-    public Set<String> getMarks(V vertex) throws NullPointerException, IllegalArgumentException {
+    public Set<Object> getMarks(V vertex) throws NullPointerException, IllegalArgumentException {
         checkNullAndExist(vertex);
         return marked.computeIfAbsent(vertex, (m) -> new HashSet<>());
     }
 
     @Override
-    public void unMarkAll(String mark) {
+    public void unMarkAll(Object mark) {
         checkNull(mark);
         marked.forEach((v, m) -> m.remove(mark));
     }
@@ -394,7 +394,7 @@ public class MapGraph<V, W extends Number> implements Graph<V, W> {
     }
 
     @Override
-    public Graph<V, W> subGraph(final String marker) {
+    public Graph<V, W> subGraph(final Object marker) {
         final Graph<V, W> graph = new MapGraph<>();
         final Set<V> allVertices = new HashSet<>();
 
diff --git a/src/berack96/sim/util/graph/Vertex.java b/src/berack96/sim/util/graph/Vertex.java
index 7c36eb6..3e29425 100644
--- a/src/berack96/sim/util/graph/Vertex.java
+++ b/src/berack96/sim/util/graph/Vertex.java
@@ -57,17 +57,29 @@ public class Vertex<V> {
      *
      * @param mark the marker
      * @throws NullPointerException          if the marker is null
-     * @throws UnsupportedOperationException if the vertes is not in the graph anymore
+     * @throws UnsupportedOperationException if the vertex is not in the graph anymore
      */
-    public void mark(String mark) throws NullPointerException, UnsupportedOperationException {
+    public void mark(Object mark) throws NullPointerException, UnsupportedOperationException {
         throwIfNotContained();
         graph.mark(vertex, mark);
     }
 
+    /**
+     * Remove the specified mark from this vertex
+     *
+     * @param mark the marker
+     * @throws NullPointerException          if the mark is null
+     * @throws UnsupportedOperationException if the vertex is not in the graph anymore
+     */
+    public void unMark(Object mark) throws UnsupportedOperationException {
+        throwIfNotContained();
+        graph.unMark(vertex, mark);
+    }
+
     /**
      * Remove all the marker from the vertex
      *
-     * @throws UnsupportedOperationException if the vertes is not in the graph anymore
+     * @throws UnsupportedOperationException if the vertex is not in the graph anymore
      */
     public void unMark() throws UnsupportedOperationException {
         throwIfNotContained();
@@ -78,9 +90,9 @@ public class Vertex<V> {
      * Get all the marks that are associated with this vertex
      *
      * @return a set of marks
-     * @throws UnsupportedOperationException if the vertes is not in the graph anymore
+     * @throws UnsupportedOperationException if the vertex is not in the graph anymore
      */
-    public Collection<String> getMarks() throws UnsupportedOperationException {
+    public Collection<Object> getMarks() throws UnsupportedOperationException {
         throwIfNotContained();
         return graph.getMarks(vertex);
     }
diff --git a/test/berack96/test/sim/TestGraph.java b/test/berack96/test/sim/TestGraph.java
index d74a29a..1b53131 100644
--- a/test/berack96/test/sim/TestGraph.java
+++ b/test/berack96/test/sim/TestGraph.java
@@ -1140,6 +1140,7 @@ public class TestGraph {
         shouldThrow(nullException, () -> vertex.addChild(null, 3));
         shouldThrow(nullException, () -> vertex.addChild(null, null));
         shouldThrow(nullException, () -> vertex.mark(null));
+        shouldThrow(nullException, () -> vertex.unMark(null));
         shouldThrow(nullException, () -> vertex.removeChild(null));
         shouldThrow(new NullPointerException(), () -> vertex.visit(null, null));
 
@@ -1185,6 +1186,13 @@ public class TestGraph {
         shouldContain(graph.getMarks(vertex.getValue()), "ciao", "ciao2");
         vertex.unMark();
         shouldContain(vertex.getMarks());
+        vertex.mark("cio");
+        vertex.mark(1);
+        shouldContain(vertex.getMarks(), "cio", 1);
+        vertex.unMark(1);
+        shouldContain(vertex.getMarks(), "cio");
+        vertex.unMark("cio");
+        shouldContain(vertex.getMarks());
 
         vertex.removeChild("1");
         shouldContain(vertex.getChildren(), "2");