diff --git a/src/list/mod.rs b/src/list/mod.rs
index 6d76bf3..264c5b5 100644
--- a/src/list/mod.rs
+++ b/src/list/mod.rs
@@ -4,6 +4,10 @@ mod unique;
 /// Defines the shared interface between the unique list (which is effectively an insert-ordered
 /// Set) and the unique list which supports removals.
 pub trait List {
+    fn new() -> Self;
+    fn with_capacity(capacity: usize) -> Self;
+    fn len(&self) -> usize;
+    fn shrink_to_fit(&mut self);
     fn append_if_new(&mut self, item: String);
     fn merge(&mut self, other: Self);
     fn merge_from(&mut self, other: &Self);
diff --git a/src/list/removable.rs b/src/list/removable.rs
index ea46d02..e23bb95 100644
--- a/src/list/removable.rs
+++ b/src/list/removable.rs
@@ -67,6 +67,30 @@ impl From<RemovableList> for Vec<String> {
 }
 
 impl List for RemovableList {
+    #[inline]
+    fn new() -> Self {
+        Self::default()
+    }
+
+    #[inline]
+    fn with_capacity(capacity: usize) -> Self {
+        Self {
+            items: Vec::with_capacity(capacity),
+            negations: vec![],
+        }
+    }
+
+    #[inline]
+    fn len(&self) -> usize {
+        self.items.len()
+    }
+
+    #[inline]
+    fn shrink_to_fit(&mut self) {
+        self.items.shrink_to_fit();
+        self.negations.shrink_to_fit();
+    }
+
     /// Appends or removes item from list
     ///
     /// Regular strings are inserted in the list if they're not present yet. When `item` is
diff --git a/src/list/unique.rs b/src/list/unique.rs
index 4de8e9d..8f57e04 100644
--- a/src/list/unique.rs
+++ b/src/list/unique.rs
@@ -44,6 +44,28 @@ impl From<UniqueList> for Vec<String> {
 }
 
 impl List for UniqueList {
+    #[inline]
+    fn new() -> Self {
+        Self::default()
+    }
+
+    #[inline]
+    fn with_capacity(capacity: usize) -> Self {
+        Self {
+            items: Vec::with_capacity(capacity),
+        }
+    }
+
+    #[inline]
+    fn len(&self) -> usize {
+        self.items.len()
+    }
+
+    #[inline]
+    fn shrink_to_fit(&mut self) {
+        self.items.shrink_to_fit();
+    }
+
     /// Appends item to list if it's not present yet
     fn append_if_new(&mut self, item: String) {
         if item_pos(&self.items, &item).is_none() {