diff --git a/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventBundle.java b/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventBundle.java
index ba3333e7f7..7361bf5d88 100644
--- a/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventBundle.java
+++ b/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventBundle.java
@@ -47,7 +47,7 @@ public interface EventBundle<ParentType extends EventBundle<?>> {
 
     Optional<ParentType> getParentBundle();
 
-    default long getCount() {
+    default int getCount() {
         return getEventIDs().size();
     }
 
diff --git a/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventCluster.java b/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventCluster.java
index 975b0cc40f..ac5a02d007 100644
--- a/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventCluster.java
+++ b/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventCluster.java
@@ -18,9 +18,9 @@
  */
 package org.sleuthkit.autopsy.timeline.datamodel;
 
+import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.ImmutableSortedSet;
 import com.google.common.collect.Sets;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.Objects;
 import java.util.Optional;
@@ -89,28 +89,28 @@ public class EventCluster implements EventBundle<EventStripe> {
     /**
      * the set of ids of the clustered events
      */
-    final private Set<Long> eventIDs;
+    final private ImmutableSet<Long> eventIDs;
 
     /**
      * the ids of the subset of clustered events that have at least one tag
      * applied to them
      */
-    private final Set<Long> tagged;
+    private final ImmutableSet<Long> tagged;
 
     /**
      * the ids of the subset of clustered events that have at least one hash set
      * hit
      */
-    private final Set<Long> hashHits;
+    private final ImmutableSet<Long> hashHits;
 
     private EventCluster(Interval spanningInterval, EventType type, Set<Long> eventIDs, Set<Long> hashHits, Set<Long> tagged, String description, DescriptionLoD lod, EventStripe parent) {
 
         this.span = spanningInterval;
         this.type = type;
-        this.hashHits = hashHits;
-        this.tagged = tagged;
+        this.hashHits = ImmutableSet.copyOf(hashHits);
+        this.tagged = ImmutableSet.copyOf(tagged);
         this.description = description;
-        this.eventIDs = eventIDs;
+        this.eventIDs = ImmutableSet.copyOf(eventIDs);
         this.lod = lod;
         this.parent = parent;
     }
@@ -139,18 +139,21 @@ public class EventCluster implements EventBundle<EventStripe> {
     }
 
     @Override
-    public Set<Long> getEventIDs() {
-        return Collections.unmodifiableSet(eventIDs);
+    @SuppressWarnings("ReturnOfCollectionOrArrayField")
+    public ImmutableSet<Long> getEventIDs() {
+        return eventIDs;
     }
 
     @Override
-    public Set<Long> getEventIDsWithHashHits() {
-        return Collections.unmodifiableSet(hashHits);
+    @SuppressWarnings("ReturnOfCollectionOrArrayField")
+    public ImmutableSet<Long> getEventIDsWithHashHits() {
+        return hashHits;
     }
 
     @Override
-    public Set<Long> getEventIDsWithTags() {
-        return Collections.unmodifiableSet(tagged);
+    @SuppressWarnings("ReturnOfCollectionOrArrayField")
+    public ImmutableSet<Long> getEventIDsWithTags() {
+        return tagged;
     }
 
     @Override
diff --git a/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventStripe.java b/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventStripe.java
index 7424727fcf..7a6bb4be42 100644
--- a/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventStripe.java
+++ b/Core/src/org/sleuthkit/autopsy/timeline/datamodel/EventStripe.java
@@ -19,13 +19,11 @@
 package org.sleuthkit.autopsy.timeline.datamodel;
 
 import com.google.common.base.Preconditions;
-import java.util.Collections;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.ImmutableSortedSet;
 import java.util.Comparator;
-import java.util.HashSet;
 import java.util.Optional;
-import java.util.Set;
 import java.util.SortedSet;
-import java.util.TreeSet;
 import javax.annotation.concurrent.Immutable;
 import org.python.google.common.base.Objects;
 import org.sleuthkit.autopsy.timeline.datamodel.eventtype.EventType;
@@ -50,7 +48,7 @@ public final class EventStripe implements EventBundle<EventCluster> {
 
     private final EventCluster parent;
 
-    private final SortedSet<EventCluster> clusters = new TreeSet<>(Comparator.comparing(EventCluster::getStartMillis));
+    private final ImmutableSortedSet<EventCluster> clusters;
 
     /**
      * the type of all the events
@@ -70,59 +68,70 @@ public final class EventStripe implements EventBundle<EventCluster> {
     /**
      * the set of ids of the events
      */
-    private final Set<Long> eventIDs = new HashSet<>();
+    private final ImmutableSet<Long> eventIDs;
 
     /**
      * the ids of the subset of events that have at least one tag applied to
      * them
      */
-    private final Set<Long> tagged = new HashSet<>();
+    private final ImmutableSet<Long> tagged;
 
     /**
      * the ids of the subset of events that have at least one hash set hit
      */
-    private final Set<Long> hashHits = new HashSet<>();
+    private final ImmutableSet<Long> hashHits;
 
     public EventStripe withParent(EventCluster parent) {
-        EventStripe eventStripe = new EventStripe(parent, this.type, this.description, this.lod);
-        eventStripe.clusters.addAll(clusters);
-        eventStripe.eventIDs.addAll(eventIDs);
-        eventStripe.tagged.addAll(tagged);
-        eventStripe.hashHits.addAll(hashHits);
+        EventStripe eventStripe = new EventStripe(parent, this.type, this.description, this.lod, clusters, eventIDs, tagged, hashHits);
         return eventStripe;
     }
 
-    private EventStripe(EventCluster parent, EventType type, String description, DescriptionLoD lod) {
+    private EventStripe(EventCluster parent, EventType type, String description, DescriptionLoD lod, SortedSet<EventCluster> clusters, ImmutableSet<Long> eventIDs, ImmutableSet<Long> tagged, ImmutableSet<Long> hashHits) {
         this.parent = parent;
         this.type = type;
         this.description = description;
         this.lod = lod;
+        this.clusters = ImmutableSortedSet.copyOf(Comparator.comparing(EventCluster::getStartMillis), clusters);
+
+        this.eventIDs = eventIDs;
+        this.tagged = tagged;
+        this.hashHits = hashHits;
     }
 
     public EventStripe(EventCluster cluster, EventCluster parent) {
-        clusters.add(cluster);
+        this.clusters = ImmutableSortedSet.orderedBy(Comparator.comparing(EventCluster::getStartMillis))
+                .add(cluster).build();
 
         type = cluster.getEventType();
         description = cluster.getDescription();
         lod = cluster.getDescriptionLoD();
-        eventIDs.addAll(cluster.getEventIDs());
-        tagged.addAll(cluster.getEventIDsWithTags());
-        hashHits.addAll(cluster.getEventIDsWithHashHits());
+        eventIDs = cluster.getEventIDs();
+        tagged = cluster.getEventIDsWithTags();
+        hashHits = cluster.getEventIDsWithHashHits();
         this.parent = parent;
     }
 
     private EventStripe(EventStripe u, EventStripe v) {
-        clusters.addAll(u.clusters);
-        clusters.addAll(v.clusters);
+        clusters = ImmutableSortedSet.orderedBy(Comparator.comparing(EventCluster::getStartMillis))
+                .addAll(u.getClusters())
+                .addAll(v.getClusters())
+                .build();
+
         type = u.getEventType();
         description = u.getDescription();
         lod = u.getDescriptionLoD();
-        eventIDs.addAll(u.getEventIDs());
-        eventIDs.addAll(v.getEventIDs());
-        tagged.addAll(u.getEventIDsWithTags());
-        tagged.addAll(v.getEventIDsWithTags());
-        hashHits.addAll(u.getEventIDsWithHashHits());
-        hashHits.addAll(v.getEventIDsWithHashHits());
+        eventIDs = ImmutableSet.<Long>builder()
+                .addAll(u.getEventIDs())
+                .addAll(v.getEventIDs())
+                .build();
+        tagged = ImmutableSet.<Long>builder()
+                .addAll(u.getEventIDsWithTags())
+                .addAll(v.getEventIDsWithTags())
+                .build();
+        hashHits = ImmutableSet.<Long>builder()
+                .addAll(u.getEventIDsWithHashHits())
+                .addAll(v.getEventIDsWithHashHits())
+                .build();
         parent = u.getParentBundle().orElse(v.getParentBundle().orElse(null));
     }
 
@@ -147,18 +156,21 @@ public final class EventStripe implements EventBundle<EventCluster> {
     }
 
     @Override
-    public Set<Long> getEventIDs() {
-        return Collections.unmodifiableSet(eventIDs);
+    @SuppressWarnings("ReturnOfCollectionOrArrayField")
+    public ImmutableSet<Long> getEventIDs() {
+        return eventIDs;
     }
 
     @Override
-    public Set<Long> getEventIDsWithHashHits() {
-        return Collections.unmodifiableSet(hashHits);
+    @SuppressWarnings("ReturnOfCollectionOrArrayField")
+    public ImmutableSet<Long> getEventIDsWithHashHits() {
+        return hashHits;
     }
 
     @Override
-    public Set<Long> getEventIDsWithTags() {
-        return Collections.unmodifiableSet(tagged);
+    @SuppressWarnings("ReturnOfCollectionOrArrayField")
+    public ImmutableSet<Long> getEventIDsWithTags() {
+        return tagged;
     }
 
     @Override
@@ -172,8 +184,9 @@ public final class EventStripe implements EventBundle<EventCluster> {
     }
 
     @Override
-    public SortedSet< EventCluster> getClusters() {
-        return Collections.unmodifiableSortedSet(clusters);
+    @SuppressWarnings("ReturnOfCollectionOrArrayField")
+    public ImmutableSortedSet< EventCluster> getClusters() {
+        return clusters;
     }
 
     @Override
diff --git a/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventClusterNode.java b/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventClusterNode.java
index 8e5c600932..f348fd6873 100644
--- a/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventClusterNode.java
+++ b/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventClusterNode.java
@@ -143,7 +143,7 @@ final public class EventClusterNode extends EventBundleNodeBase<EventCluster, Ev
 
     @Override
     void setDescriptionVisibiltiyImpl(DescriptionVisibility descrVis) {
-        final int size = getEventBundle().getEventIDs().size();
+        final int size = getEventCluster().getCount();
         switch (descrVis) {
             case HIDDEN:
                 countLabel.setText("");
diff --git a/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventStripeNode.java b/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventStripeNode.java
index f6861735bd..dde8cb03c4 100644
--- a/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventStripeNode.java
+++ b/Core/src/org/sleuthkit/autopsy/timeline/ui/detailview/EventStripeNode.java
@@ -68,13 +68,13 @@ final public class EventStripeNode extends EventBundleNodeBase<EventStripe, Even
         super(chart, eventStripe, parentNode);
 
         setMinHeight(48);
-
         //setup description label
         eventTypeImageView.setImage(getEventType().getFXImage());
         descrLabel.setTextOverrun(OverrunStyle.CENTER_ELLIPSIS);
         descrLabel.setGraphic(eventTypeImageView);
         descrLabel.setPrefWidth(USE_COMPUTED_SIZE);
         setAlignment(subNodePane, Pos.BOTTOM_LEFT);
+
         for (EventCluster cluster : eventStripe.getClusters()) {
             subNodes.add(createChildNode(cluster));
         }
@@ -124,7 +124,7 @@ final public class EventStripeNode extends EventBundleNodeBase<EventStripe, Even
 
     @Override
     void setDescriptionVisibiltiyImpl(DescriptionVisibility descrVis) {
-        final int size = getEventStripe().getEventIDs().size();
+        final int size = getEventStripe().getCount();
 
         switch (descrVis) {
             case HIDDEN: