diff --git a/src/main/java/com/songoda/skyblock/listeners/Interact.java b/src/main/java/com/songoda/skyblock/listeners/Interact.java
index 2aa4395c..eac79954 100644
--- a/src/main/java/com/songoda/skyblock/listeners/Interact.java
+++ b/src/main/java/com/songoda/skyblock/listeners/Interact.java
@@ -141,7 +141,7 @@ public class Interact implements Listener {
 
         if (event.getAction() == Action.RIGHT_CLICK_BLOCK) {
             if (stackableManager != null
-                    && stackableManager.getStackableMaterials().contains(event.getMaterial())
+                    && stackableManager.isStackableMaterial(event.getMaterial())
                     && event.getClickedBlock().getType() == event.getMaterial()
                     && !player.isSneaking() && islandManager.hasPermission(player, block.getLocation(), "Place")
                     && (!skyblock.getFileManager().getConfig(new File(skyblock.getDataFolder(), "config.yml")).getFileConfiguration().getBoolean("Island.Stackable.RequirePermission") || player.hasPermission("fabledskyblock.stackable"))) {
diff --git a/src/main/java/com/songoda/skyblock/stackable/StackableManager.java b/src/main/java/com/songoda/skyblock/stackable/StackableManager.java
index 9418526a..4f4bb160 100644
--- a/src/main/java/com/songoda/skyblock/stackable/StackableManager.java
+++ b/src/main/java/com/songoda/skyblock/stackable/StackableManager.java
@@ -15,7 +15,7 @@ public class StackableManager {
     //ToDO: Should pobably be a GUI for this
 
     private final SkyBlock skyblock;
-    private List<Material> stackableMaterials = new ArrayList<>();
+    private Set<Material> stackableMaterials = EnumSet.noneOf(Material.class);
     private Map<Location, Stackable> stacks = new HashMap<>();
 
     public StackableManager(SkyBlock skyblock) {
@@ -66,8 +66,8 @@ public class StackableManager {
         stackableMaterials.clear();
     }
 
-    public List<Material> getStackableMaterials() {
-        return Collections.unmodifiableList(stackableMaterials);
+    public Set<Material> getStackableMaterials() {
+        return Collections.unmodifiableSet(stackableMaterials);
     }
     
     public boolean isStackableMaterial(Material material) {