diff --git a/eco-api/src/main/java/com/willfp/eco/core/fast/FastItemStack.java b/eco-api/src/main/java/com/willfp/eco/core/fast/FastItemStack.java
index ac7688bb..27caace2 100644
--- a/eco-api/src/main/java/com/willfp/eco/core/fast/FastItemStack.java
+++ b/eco-api/src/main/java/com/willfp/eco/core/fast/FastItemStack.java
@@ -9,6 +9,10 @@ import java.util.Map;
 
 /**
  * FastItemStack contains methods to modify and read items faster than in default bukkit.
+ * <p>
+ * If the ItemStack wrapped is a CraftItemStack, then the instance will be modified, allowing for set methods to work.
+ * <p>
+ * Otherwise, the FastItemStack must then be unwrapped to get a bukkit copy.
  */
 public interface FastItemStack {
     /**
@@ -29,6 +33,22 @@ public interface FastItemStack {
     int getLevelOnItem(@NotNull Enchantment enchantment,
                        boolean checkStored);
 
+    /**
+     * Unwrap an ItemStack.
+     *
+     * @return The bukkit ItemStack.
+     */
+    ItemStack unwrap();
+
+    /**
+     * If the FastItemStack modifies the actual ItemStack instance or a copy.
+     * <p>
+     * If a copy, then {@link FastItemStack#unwrap()} must be called in order to obtain the modified Bukkit ItemStack.
+     *
+     * @return If the ItemStack wrapped is a CraftItemStack, allowing for direct modification.
+     */
+    boolean isModifyingInstance();
+
     /**
      * Wrap an ItemStack to create a FastItemStack.
      *
diff --git a/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/EcoFastItemStack.java b/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/EcoFastItemStack.java
index 0f71f71e..c148e5a1 100644
--- a/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/EcoFastItemStack.java
+++ b/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/EcoFastItemStack.java
@@ -7,6 +7,7 @@ import net.minecraft.server.v1_16_R3.Items;
 import net.minecraft.server.v1_16_R3.NBTBase;
 import net.minecraft.server.v1_16_R3.NBTTagCompound;
 import net.minecraft.server.v1_16_R3.NBTTagList;
+import org.bukkit.craftbukkit.v1_16_R3.inventory.CraftItemStack;
 import org.bukkit.craftbukkit.v1_16_R3.util.CraftNamespacedKey;
 import org.bukkit.enchantments.Enchantment;
 import org.jetbrains.annotations.NotNull;
@@ -16,9 +17,11 @@ import java.util.Map;
 
 public class EcoFastItemStack implements FastItemStack {
     private final ItemStack handle;
+    private final boolean isCMS;
 
     public EcoFastItemStack(@NotNull final org.bukkit.inventory.ItemStack itemStack) {
         this.handle = FastItemStackUtils.getNMSStack(itemStack);
+        this.isCMS = itemStack instanceof CraftItemStack;
     }
 
     @Override
@@ -55,4 +58,14 @@ public class EcoFastItemStack implements FastItemStack {
         }
         return 0;
     }
+
+    @Override
+    public org.bukkit.inventory.ItemStack unwrap() {
+        return CraftItemStack.asCraftMirror(handle);
+    }
+
+    @Override
+    public boolean isModifyingInstance() {
+        return isCMS;
+    }
 }
diff --git a/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/FastItemStackUtils.java b/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/FastItemStackUtils.java
index 49e4ac3e..67d6407a 100644
--- a/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/FastItemStackUtils.java
+++ b/eco-core/core-nms/v1_16_R3/src/main/java/com/willfp/eco/proxy/v1_16_R3/fast/FastItemStackUtils.java
@@ -1,6 +1,7 @@
 package com.willfp.eco.proxy.v1_16_R3.fast;
 
 import lombok.experimental.UtilityClass;
+import org.bukkit.Bukkit;
 import org.bukkit.craftbukkit.libs.org.apache.commons.lang3.Validate;
 import org.bukkit.craftbukkit.v1_16_R3.inventory.CraftItemStack;
 import org.bukkit.inventory.ItemStack;
@@ -13,8 +14,9 @@ public class FastItemStackUtils {
     private final Field field;
 
     public net.minecraft.server.v1_16_R3.ItemStack getNMSStack(@NotNull final ItemStack itemStack) {
-        if (itemStack instanceof CraftItemStack) {
-            throw new IllegalArgumentException("Must be CraftItemStack!");
+        if (!(itemStack instanceof CraftItemStack)) {
+            Bukkit.getLogger().warning("Not CraftItemStack - set methods will not work!");
+            return CraftItemStack.asNMSCopy(itemStack);
         }
         try {
             return (net.minecraft.server.v1_16_R3.ItemStack) field.get(itemStack);
diff --git a/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/EcoFastItemStack.java b/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/EcoFastItemStack.java
index 46b3f43b..62be6e31 100644
--- a/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/EcoFastItemStack.java
+++ b/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/EcoFastItemStack.java
@@ -7,6 +7,7 @@ import net.minecraft.nbt.Tag;
 import net.minecraft.world.item.EnchantedBookItem;
 import net.minecraft.world.item.ItemStack;
 import net.minecraft.world.item.Items;
+import org.bukkit.craftbukkit.v1_17_R1.inventory.CraftItemStack;
 import org.bukkit.craftbukkit.v1_17_R1.util.CraftNamespacedKey;
 import org.bukkit.enchantments.Enchantment;
 import org.jetbrains.annotations.NotNull;
@@ -16,9 +17,11 @@ import java.util.Map;
 
 public class EcoFastItemStack implements FastItemStack {
     private final ItemStack handle;
+    private final boolean isCMS;
 
     public EcoFastItemStack(@NotNull final org.bukkit.inventory.ItemStack itemStack) {
         this.handle = FastItemStackUtils.getNMSStack(itemStack);
+        this.isCMS = itemStack instanceof CraftItemStack;
     }
 
     @Override
@@ -55,4 +58,14 @@ public class EcoFastItemStack implements FastItemStack {
         }
         return 0;
     }
+
+    @Override
+    public org.bukkit.inventory.ItemStack unwrap() {
+        return CraftItemStack.asCraftMirror(handle);
+    }
+
+    @Override
+    public boolean isModifyingInstance() {
+        return isCMS;
+    }
 }
diff --git a/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/FastItemStackUtils.java b/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/FastItemStackUtils.java
index c237a816..53bba999 100644
--- a/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/FastItemStackUtils.java
+++ b/eco-core/core-nms/v1_17_R1/src/main/java/com/willfp/eco/proxy/v1_17_R1/fast/FastItemStackUtils.java
@@ -1,6 +1,7 @@
 package com.willfp.eco.proxy.v1_17_R1.fast;
 
 import lombok.experimental.UtilityClass;
+import org.bukkit.Bukkit;
 import org.bukkit.craftbukkit.libs.org.apache.commons.lang3.Validate;
 import org.bukkit.craftbukkit.v1_17_R1.inventory.CraftItemStack;
 import org.bukkit.inventory.ItemStack;
@@ -13,8 +14,9 @@ public class FastItemStackUtils {
     private final Field field;
 
     public net.minecraft.world.item.ItemStack getNMSStack(@NotNull final ItemStack itemStack) {
-        if (itemStack instanceof CraftItemStack) {
-            throw new IllegalArgumentException("Must be CraftItemStack!");
+        if (!(itemStack instanceof CraftItemStack)) {
+            Bukkit.getLogger().warning("Not CraftItemStack - set methods will not work!");
+            return CraftItemStack.asNMSCopy(itemStack);
         }
         try {
             return (net.minecraft.world.item.ItemStack) field.get(itemStack);