diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/ConfigDelegates.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/ConfigDelegates.kt
index e848ec31..39a5f569 100644
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/ConfigDelegates.kt
+++ b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/ConfigDelegates.kt
@@ -10,25 +10,19 @@ import kotlin.jvm.JvmName
 /**
  * A property delegate that uses custom key
  */
-fun Configurable.value(default: Any = Null, key: String? = null) =
+fun Configurable.value(default: Any = Null, key: String? = null): MutableValueDelegate<Config> =
     MutableValueDelegate(config, key, Value.of(default))
 
-fun <T> Configurable.value(default: T? = null, key: String? = null, transform: (Value?) -> T) =
+fun <T> Configurable.value(default: T? = null, key: String? = null, transform: (Value?) -> T): ReadWriteDelegateWrapper<Value?, T> =
     MutableValueDelegate(config, key, Value.of(default)).transform(reader = transform)
 
-fun Configurable.stringList(key: String? = null) =
-    value(key) { it?.list?.map { value -> value.string } ?: emptyList() }
-
-fun Configurable.numberList(key: String? = null) =
-    value(key) { it?.list?.map { value -> value.number } ?: emptyList() }
-
-fun Configurable.string(default: String? = null, key: String? = null) =
+fun Configurable.string(default: String? = null, key: String? = null): MutableStringDelegate<Config> =
     MutableStringDelegate(config, key, default)
 
-fun Configurable.boolean(default: Boolean? = null, key: String? = null) =
+fun Configurable.boolean(default: Boolean? = null, key: String? = null): MutableBooleanDelegate<Config> =
     MutableBooleanDelegate(config, key, default)
 
-fun Configurable.number(default: Number? = null, key: String? = null) =
+fun Configurable.number(default: Number? = null, key: String? = null): MutableNumberDelegate<Config> =
     MutableNumberDelegate(config, key, default)
 
 /* Number delegates*/
@@ -111,3 +105,19 @@ fun <T : Specific> Configurable.spec(spec: Specification<T>, key: String? = null
 
 fun <T : Specific> Configurable.spec(builder: (Config) -> T, key: String? = null) =
     MutableMorphDelegate(config, key) { specification(builder).wrap(it) }
+
+
+/*
+ * Extra delegates for special cases
+ */
+
+fun Configurable.stringList(key: String? = null): ReadWriteDelegateWrapper<Value?, List<String>> =
+    value(emptyList(), key) { it?.list?.map { value -> value.string } ?: emptyList() }
+
+fun Configurable.numberList(key: String? = null): ReadWriteDelegateWrapper<Value?, List<Number>> =
+    value(emptyList(), key) { it?.list?.map { value -> value.number } ?: emptyList() }
+
+fun <T : Metoid> Metoid.child(key: String? = null, converter: (Meta) -> T) = ChildDelegate(meta, key, converter)
+
+fun <T : Configurable> Configurable.child(key: String? = null, converter: (Meta) -> T) =
+    MutableMorphDelegate(config, key, converter)
diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/ExtraMetaDelegates.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/ExtraMetaDelegates.kt
deleted file mode 100644
index 6e24c6d0..00000000
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/ExtraMetaDelegates.kt
+++ /dev/null
@@ -1,36 +0,0 @@
-package hep.dataforge.meta
-
-import kotlin.properties.ReadWriteProperty
-import kotlin.reflect.KProperty
-
-/*
- * Extra delegates for special cases
- */
-
-/**
- * A delegate for a string list
- */
-class StringListConfigDelegate(
-    val config: Config,
-    private val key: String? = null,
-    private val default: List<String> = emptyList()
-) :
-    ReadWriteProperty<Any?, List<String>> {
-    override fun getValue(thisRef: Any?, property: KProperty<*>): List<String> {
-        return config[key ?: property.name]?.value?.list?.map { it.string } ?: default
-    }
-
-    override fun setValue(thisRef: Any?, property: KProperty<*>, value: List<String>) {
-        val name = key ?: property.name
-        config[name] = value
-    }
-}
-
-fun Configurable.stringList(vararg default: String = emptyArray(), key: String? = null) =
-    StringListConfigDelegate(config, key, default.toList())
-
-
-fun <T : Metoid> Metoid.child(key: String? = null, converter: (Meta) -> T) = ChildDelegate(meta, key, converter)
-
-fun <T : Configurable> Configurable.child(key: String? = null, converter: (Meta) -> T) =
-    MutableMorphDelegate(config, key, converter)
diff --git a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/Specific.kt b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/Specific.kt
index 10210fb4..a89a44a1 100644
--- a/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/Specific.kt
+++ b/dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/Specific.kt
@@ -1,11 +1,13 @@
 package hep.dataforge.meta
 
 /**
- * Marker interface for specifications
+ * Marker interface for classes with specifications
  */
-interface Specific : Configurable {
-    operator fun get(name: String): MetaItem<Config>? = config[name]
-}
+interface Specific : Configurable
+
+//TODO separate mutable config from immutable meta to allow free wrapping of meta
+
+operator fun Specific.get(name: String): MetaItem<*>? = config[name]
 
 /**
  * Allows to apply custom configuration in a type safe way to simple untyped configuration.
@@ -29,6 +31,7 @@ interface Specification<T : Specific> {
      */
     fun wrap(config: Config): T
 
+    //TODO replace by free wrapper
     fun wrap(meta: Meta): T = wrap(meta.toConfig())
 }
 
@@ -59,4 +62,4 @@ fun <C : Specific, S : Specification<C>> S.createStyle(action: C.() -> Unit): Me
 fun <C : Specific> Specific.spec(
     spec: Specification<C>,
     key: String? = null
-) = MutableMorphDelegate(config, key) { spec.wrap(it) }
\ No newline at end of file
+): MutableMorphDelegate<Config, C> = MutableMorphDelegate(config, key) { spec.wrap(it) }
\ No newline at end of file