diff --git a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/EcoArmorPlugin.kt b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/EcoArmorPlugin.kt
index 58a4ea3..3fcb599 100644
--- a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/EcoArmorPlugin.kt
+++ b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/EcoArmorPlugin.kt
@@ -4,6 +4,7 @@ import com.willfp.eco.core.EcoPlugin
 import com.willfp.eco.core.command.impl.PluginCommand
 import com.willfp.eco.core.display.DisplayModule
 import com.willfp.eco.core.integrations.IntegrationLoader
+import com.willfp.eco.util.ListUtils
 import com.willfp.ecoarmor.commands.CommandEcoarmor
 import com.willfp.ecoarmor.config.EcoArmorYml
 import com.willfp.ecoarmor.display.ArmorDisplay
@@ -31,14 +32,7 @@ class EcoArmorPlugin : EcoPlugin(687, 10002, "&c") {
         instance = this
         ecoArmorYml = EcoArmorYml(this)
         init(this)
-        registerHolderProvider { player ->
-            val active = ArmorUtils.getActiveSet(player)
-            if (active == null) {
-                emptyList()
-            } else {
-                listOf(active)
-            }
-        }
+        registerHolderProvider { ListUtils.toSingletonList(ArmorUtils.getActiveSet(it)) }
     }
 
     override fun handleEnable() {
diff --git a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/AdvancedHolder.kt b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/AdvancedHolder.kt
deleted file mode 100644
index dde6ef7..0000000
--- a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/AdvancedHolder.kt
+++ /dev/null
@@ -1,10 +0,0 @@
-package com.willfp.ecoarmor.sets
-
-import com.willfp.libreforge.Holder
-import com.willfp.libreforge.conditions.ConfiguredCondition
-import com.willfp.libreforge.effects.ConfiguredEffect
-
-class AdvancedHolder(
-    override val conditions: Set<ConfiguredCondition>,
-    override val effects: Set<ConfiguredEffect>) : Holder {
-}
diff --git a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/ArmorSet.kt b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/ArmorSet.kt
index bef3461..0380a8d 100644
--- a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/ArmorSet.kt
+++ b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/ArmorSet.kt
@@ -16,6 +16,7 @@ import com.willfp.ecoarmor.sets.ArmorUtils.setAdvanced
 import com.willfp.ecoarmor.sets.ArmorUtils.setTier
 import com.willfp.ecoarmor.upgrades.Tier
 import com.willfp.ecoarmor.upgrades.Tiers
+import com.willfp.ecoarmor.util.notNullMapOf
 import com.willfp.libreforge.Holder
 import com.willfp.libreforge.conditions.Conditions
 import com.willfp.libreforge.conditions.ConfiguredCondition
@@ -51,12 +52,12 @@ class ArmorSet(
     /**
      * Items in set.
      */
-    private val items: MutableMap<ArmorSlot, ItemStack> = EnumMap(ArmorSlot::class.java)
+    private val items = notNullMapOf<ArmorSlot, ItemStack>()
 
     /**
      * Items in advanced set.
      */
-    private val advancedItems: MutableMap<ArmorSlot, ItemStack> = EnumMap(ArmorSlot::class.java)
+    private val advancedItems = notNullMapOf<ArmorSlot, ItemStack>()
 
     /**
      * Advancement shard item.
@@ -88,8 +89,8 @@ class ArmorSet(
                 advancedEffects.add(conf)
             }
         }
-        regularHolder = RegularHolder(conditions, effects)
-        advancedHolder = AdvancedHolder(conditions, advancedEffects)
+        regularHolder = SimpleHolder(conditions, effects)
+        advancedHolder = SimpleHolder(conditions, advancedEffects)
         ArmorSets.addNewSet(this)
         for (slot in ArmorSlot.values()) {
             val item = construct(slot, config.getSubsection(slot.name.lowercase(Locale.getDefault())), false)
@@ -105,9 +106,7 @@ class ArmorSet(
         val shardLore = config.getStrings("advancementShardLore")
         shardLore.replaceAll { Display.PREFIX + it }
         val shard = ItemStackBuilder(
-            Items.lookup(
-                plugin.configYml.getString("advancement-shard-material").lowercase(Locale.getDefault())
-            ).item
+            Items.lookup(plugin.configYml.getString("advancement-shard-material"))
         )
             .setDisplayName(config.getString("advancementShardName"))
             .addEnchantment(Enchantment.DURABILITY, 3)
@@ -240,7 +239,7 @@ class ArmorSet(
      * @return The item.
      */
     fun getItemStack(slot: ArmorSlot): ItemStack {
-        return items[slot]!!
+        return items[slot]
     }
 
     /**
@@ -250,7 +249,7 @@ class ArmorSet(
      * @return The item.
      */
     fun getAdvancedItemStack(slot: ArmorSlot): ItemStack {
-        return advancedItems[slot]!!
+        return advancedItems[slot]
     }
 
     /**
@@ -260,16 +259,12 @@ class ArmorSet(
      * @return The tier.
      */
     fun getDefaultTier(slot: ArmorSlot?): Tier {
-        if (slot == null) return Tiers.defaultTier
+        slot ?: return Tiers.defaultTier
         val tier = Tiers.getByID(config.getSubsection(slot.name.lowercase()).getString("defaultTier"))
         return tier ?: Tiers.defaultTier
     }
 
     override fun equals(other: Any?): Boolean {
-        if (this === other) {
-            return true
-        }
-
         if (other !is ArmorSet) {
             return false
         }
@@ -286,4 +281,9 @@ class ArmorSet(
                 + id
                 + "}")
     }
-}
\ No newline at end of file
+}
+
+class SimpleHolder(
+    override val conditions: Set<ConfiguredCondition>,
+    override val effects: Set<ConfiguredEffect>
+) : Holder
\ No newline at end of file
diff --git a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/RegularHolder.kt b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/RegularHolder.kt
deleted file mode 100644
index e851e4f..0000000
--- a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/sets/RegularHolder.kt
+++ /dev/null
@@ -1,10 +0,0 @@
-package com.willfp.ecoarmor.sets
-
-import com.willfp.libreforge.Holder
-import com.willfp.libreforge.conditions.ConfiguredCondition
-import com.willfp.libreforge.effects.ConfiguredEffect
-
-class RegularHolder(
-    override val conditions: Set<ConfiguredCondition>,
-    override val effects: Set<ConfiguredEffect>) : Holder {
-}
diff --git a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/CrystalListener.kt b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/CrystalListener.kt
index 8c91fde..6a4754a 100644
--- a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/CrystalListener.kt
+++ b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/CrystalListener.kt
@@ -30,8 +30,8 @@ class CrystalListener(private val plugin: EcoPlugin) : Listener {
         }
         val previousTier = ArmorUtils.getTier(current)
         var allowed = false
-        val prereq = crystalTier.getRequiredTiersForApplication()
-        if (prereq.isEmpty() || prereq.contains(previousTier)) {
+        val requiredTiers = crystalTier.getRequiredTiersForApplication()
+        if (requiredTiers.isEmpty() || requiredTiers.contains(previousTier)) {
             allowed = true
         }
         if (!allowed) {
diff --git a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/Tier.kt b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/Tier.kt
index 12f35ad..a999b59 100644
--- a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/Tier.kt
+++ b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/upgrades/Tier.kt
@@ -10,24 +10,19 @@ import com.willfp.eco.core.recipe.recipes.ShapedCraftingRecipe
 import com.willfp.eco.util.StringUtils
 import com.willfp.ecoarmor.sets.ArmorSlot
 import com.willfp.ecoarmor.sets.ArmorUtils.getCrystalTier
-import com.willfp.ecoarmor.util.NotNullMap
+import com.willfp.ecoarmor.util.notNullMapOf
 import org.bukkit.inventory.ItemStack
 import org.bukkit.persistence.PersistentDataType
 import java.util.*
 
 class Tier(
-    config: Config,
+    private val config: Config,
     plugin: EcoPlugin
 ) : PluginDependent<EcoPlugin?>(plugin) {
     /**
      * The tier name.
      */
-    val id: String
-
-    /**
-     * The config of the crystal.
-     */
-    val config: Config
+    val id = config.getString("id")
 
     /**
      * The display name of the crystal.
@@ -57,16 +52,14 @@ class Tier(
     /**
      * Item properties.
      */
-    val properties: NotNullMap<ArmorSlot, TierProperties> = NotNullMap(EnumMap(ArmorSlot::class.java))
+    val properties = notNullMapOf<ArmorSlot, TierProperties>()
 
     /**
      * Create a new Tier.
      */
     init {
-        id = config.getString("id")
-        this.config = config
         Tiers.addNewTier(this)
-        
+
         craftable = this.config.getBool("crystal.craftable")
         displayName = this.config.getString("display")
         requiredTiersForApplication = this.config.getStrings("requiresTiers")
@@ -101,11 +94,13 @@ class Tier(
                     .getInt("properties." + slot.name.lowercase(Locale.getDefault()) + ".attackKnockbackPercentage")
             )
         }
+
         CustomItem(
             plugin.namespacedKeyFactory.create("crystal_" + id.lowercase(Locale.getDefault())),
             { test: ItemStack? -> this == getCrystalTier(test!!) },
             out
         ).register()
+
         if (this.craftable) {
             val recipeOut = out.clone()
             recipeOut.amount = this.config.getInt("crystal.giveAmount")
@@ -130,6 +125,7 @@ class Tier(
             crystalRecipe = null
         }
     }
+
     /**
      * Get the required tiers for application.
      *
diff --git a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/util/NotNullMap.kt b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/util/NotNullMap.kt
index 77c6958..908228d 100644
--- a/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/util/NotNullMap.kt
+++ b/eco-core/core-plugin/src/main/kotlin/com/willfp/ecoarmor/util/NotNullMap.kt
@@ -4,4 +4,13 @@ class NotNullMap<K, V>(private val handle: MutableMap<K, V>) : MutableMap<K, V>
     override fun get(key: K): V {
         return handle[key]!!
     }
-}
\ No newline at end of file
+}
+
+inline fun <reified K, reified V> Map<K, V>.toNotNullMap(): NotNullMap<K, V> =
+    NotNullMap(this.toMutableMap())
+
+inline fun <reified K, reified V> notNullMapOf(): NotNullMap<K, V> =
+    mutableMapOf<K, V>().toNotNullMap()
+
+inline fun <reified K, reified V> notNullMapOf(vararg pairs: Pair<K, V>): NotNullMap<K, V> =
+    mutableMapOf(*pairs).toNotNullMap()
\ No newline at end of file