diff --git a/src/impls/deduplicate.rs b/src/impls/deduplicate.rs
index 2f4cda2..35c1ab6 100644
--- a/src/impls/deduplicate.rs
+++ b/src/impls/deduplicate.rs
@@ -1,7 +1,8 @@
 //! Simple deduplication of equal consecutive items.
 
-use crate::impls::offsets::OffsetContainer;
+use crate::impls::offsets::{OffsetContainer, OffsetRegion};
 use crate::{CopyOnto, Region};
+use crate::impls::vec::CopyVector;
 
 /// A region to deduplicate consecutive equal items.
 #[derive(Debug, Clone)]
@@ -79,10 +80,10 @@ where
 /// Defers to region `R` for storing items, and uses offset container `O` to
 /// rember indices. By default, `O` is `Vec<usize>`.
 #[derive(Debug, Clone)]
-pub struct ConsecutiveOffsetPairs<R, O = Vec<usize>>
+pub struct ConsecutiveOffsetPairs<R, O = CopyVector<usize>>
 where
     R: Region<Index = (usize, usize)>,
-    O: OffsetContainer<usize>,
+    O: OffsetRegion, usize: CopyOnto<O>,
 {
     /// Wrapped region
     inner: R,
@@ -92,8 +93,9 @@ where
     last_index: usize,
 }
 
-impl<R: Region<Index = (usize, usize)>, O: OffsetContainer<usize>> Default
+impl<R: Region<Index = (usize, usize)>, O: OffsetRegion> Default
     for ConsecutiveOffsetPairs<R, O>
+where usize: CopyOnto<O>,
 {
     fn default() -> Self {
         let mut d = Self {
@@ -101,13 +103,14 @@ impl<R: Region<Index = (usize, usize)>, O: OffsetContainer<usize>> Default
             offsets: Default::default(),
             last_index: 0,
         };
-        d.offsets.push(0);
+        0.copy_onto(&mut d.offsets);
         d
     }
 }
 
-impl<R: Region<Index = (usize, usize)>, O: OffsetContainer<usize>> Region
+impl<R: Region<Index = (usize, usize)>, O: OffsetRegion> Region
     for ConsecutiveOffsetPairs<R, O>
+    where usize: CopyOnto<O>,
 {
     type ReadItem<'a> = R::ReadItem<'a>
     where
@@ -120,7 +123,7 @@ impl<R: Region<Index = (usize, usize)>, O: OffsetContainer<usize>> Region
         Self: 'a,
     {
         let mut offsets = O::default();
-        offsets.push(0);
+        0.copy_onto(&mut offsets);
         Self {
             inner: R::merge_regions(regions.clone().map(|r| &r.inner)),
             offsets,
@@ -145,12 +148,13 @@ impl<R: Region<Index = (usize, usize)>, O: OffsetContainer<usize>> Region
         self.last_index = 0;
         self.inner.clear();
         self.offsets.clear();
-        self.offsets.push(0);
+        0.copy_onto(&mut self.offsets);
     }
 }
 
-impl<R: Region<Index = (usize, usize)>, O: OffsetContainer<usize>, T: CopyOnto<R>>
+impl<R: Region<Index = (usize, usize)>, O: OffsetRegion, T: CopyOnto<R>>
     CopyOnto<ConsecutiveOffsetPairs<R, O>> for T
+    where usize: CopyOnto<O>,
 {
     fn copy_onto(
         self,
@@ -159,7 +163,7 @@ impl<R: Region<Index = (usize, usize)>, O: OffsetContainer<usize>, T: CopyOnto<R
         let index = self.copy_onto(&mut target.inner);
         debug_assert_eq!(index.0, target.last_index);
         target.last_index = index.1;
-        target.offsets.push(index.1);
+        index.1.copy_onto(&mut target.offsets);
         target.offsets.len() - 2
     }
 }
diff --git a/src/impls/mod.rs b/src/impls/mod.rs
index fdcf043..3ab05c6 100644
--- a/src/impls/mod.rs
+++ b/src/impls/mod.rs
@@ -10,3 +10,4 @@ pub mod slice;
 pub mod slice_copy;
 pub mod string;
 pub mod tuple;
+pub mod vec;
diff --git a/src/impls/offsets.rs b/src/impls/offsets.rs
index c0811f5..2cc4079 100644
--- a/src/impls/offsets.rs
+++ b/src/impls/offsets.rs
@@ -1,5 +1,18 @@
 //! Types to represent offsets.
 
+use crate::{CopyOnto, Region};
+
+pub trait OffsetRegion
+where
+    for<'a> Self: Region<ReadItem<'a> = usize, Index=usize> + 'a,
+    usize: CopyOnto<Self>,
+{
+}
+
+impl<R> OffsetRegion for R where for<'a> Self: Region<ReadItem<'a> = usize, Index=usize> + 'a,
+usize: CopyOnto<Self>,
+{}
+
 /// TODO
 pub trait OffsetContainer<T>: Default + Extend<T> {
     /// Accepts a newly pushed element.
@@ -101,29 +114,69 @@ impl OffsetStride {
 /// A list of unsigned integers that uses `u32` elements as long as they are small enough, and switches to `u64` once they are not.
 #[derive(Eq, PartialEq, Ord, PartialOrd, Clone, Debug, Default)]
 pub struct OffsetList {
-    /// Length of a prefix of zero elements.
-    pub zero_prefix: usize,
     /// Offsets that fit within a `u32`.
     pub smol: Vec<u32>,
     /// Offsets that either do not fit in a `u32`, or are inserted after some offset that did not fit.
     pub chonk: Vec<u64>,
 }
 
+impl Region for OffsetList {
+    type ReadItem<'a> = usize where Self: 'a;
+    type Index = usize;
+
+    fn merge_regions<'a>(regions: impl Iterator<Item = &'a Self> + Clone) -> Self
+    where
+        Self: 'a,
+    {
+        Self {
+            smol: Vec::with_capacity(regions.clone().map(|r| r.smol.len()).sum()),
+            chonk: Vec::with_capacity(regions.clone().map(|r| r.chonk.len()).sum()),
+        }
+    }
+
+    fn index(&self, index: Self::Index) -> Self::ReadItem<'_> {
+        if index < self.smol.len() {
+            self.smol[index].try_into().unwrap()
+        } else {
+            self.chonk[index - self.smol.len()].try_into().unwrap()
+        }
+    }
+
+    fn reserve_regions<'a, I>(&mut self, regions: I)
+    where
+        Self: 'a,
+        I: Iterator<Item = &'a Self> + Clone,
+    {
+        self.smol
+            .reserve(regions.clone().map(|r| r.smol.len()).sum());
+        self.chonk
+            .reserve(regions.clone().map(|r| r.chonk.len()).sum());
+    }
+
+    fn clear(&mut self) {
+        self.clear();
+    }
+}
+
+impl CopyOnto<OffsetList> for usize {
+    fn copy_onto(self, target: &mut OffsetList) -> usize {
+        target.push(self);
+        target.len() - 1
+    }
+}
+
 impl OffsetList {
     // TODO
     // /// Allocate a new list with a specified capacity.
     // pub fn with_capacity(cap: usize) -> Self {
     //     Self {
-    //         zero_prefix: 0,
     //         smol: Vec::with_capacity(cap),
     //         chonk: Vec::new(),
     //     }
     // }
     /// Inserts the offset, as a `u32` if that is still on the table.
     pub fn push(&mut self, offset: usize) {
-        if self.smol.is_empty() && self.chonk.is_empty() && offset == 0 {
-            self.zero_prefix += 1;
-        } else if self.chonk.is_empty() {
+        if self.chonk.is_empty() {
             if let Ok(smol) = offset.try_into() {
                 self.smol.push(smol);
             } else {
@@ -133,21 +186,17 @@ impl OffsetList {
             self.chonk.push(offset.try_into().unwrap())
         }
     }
-    /// Like `std::ops::Index`, which we cannot implement as it must return a `&usize`.
-    pub fn index(&self, index: usize) -> usize {
-        if index < self.zero_prefix {
-            0
-        } else if index - self.zero_prefix < self.smol.len() {
-            self.smol[index - self.zero_prefix].try_into().unwrap()
-        } else {
-            self.chonk[index - self.zero_prefix - self.smol.len()]
-                .try_into()
-                .unwrap()
-        }
-    }
+    // /// Like `std::ops::Index`, which we cannot implement as it must return a `&usize`.
+    // pub fn index(&self, index: usize) -> usize {
+    //     if index < self.smol.len() {
+    //         self.smol[index].try_into().unwrap()
+    //     } else {
+    //         self.chonk[index - self.smol.len()].try_into().unwrap()
+    //     }
+    // }
     /// The number of offsets in the list.
     pub fn len(&self) -> usize {
-        self.zero_prefix + self.smol.len() + self.chonk.len()
+        self.smol.len() + self.chonk.len()
     }
 
     /// Returns `true` if this list contains no elements.
@@ -174,6 +223,49 @@ pub struct OffsetOptimized {
     spilled: OffsetList,
 }
 
+impl Region for OffsetOptimized {
+    type ReadItem<'a> = usize where Self: 'a;
+    type Index = usize;
+
+    fn merge_regions<'a>(regions: impl Iterator<Item = &'a Self> + Clone) -> Self
+    where
+        Self: 'a,
+    {
+        Self {
+            strided: OffsetStride::default(),
+            spilled: OffsetList::merge_regions(regions.map(|r| &r.spilled)),
+        }
+    }
+
+    fn index(&self, index: Self::Index) -> Self::ReadItem<'_> {
+        if index < self.strided.len() {
+            self.strided.index(index)
+        } else {
+            self.spilled.index(index - self.strided.len())
+        }
+    }
+
+    fn reserve_regions<'a, I>(&mut self, regions: I)
+    where
+        Self: 'a,
+        I: Iterator<Item = &'a Self> + Clone,
+    {
+        self.spilled.reserve_regions(regions.map(|r| &r.spilled));
+    }
+
+    fn clear(&mut self) {
+        self.strided = OffsetStride::default();
+        self.spilled.clear();
+    }
+}
+
+impl CopyOnto<OffsetOptimized> for usize {
+    fn copy_onto(self, target: &mut OffsetOptimized) -> usize {
+        target.push(self);
+        target.len() - 1
+    }
+}
+
 impl OffsetContainer<usize> for OffsetOptimized {
     fn push(&mut self, item: usize) {
         if !self.spilled.is_empty() {
@@ -195,8 +287,8 @@ impl OffsetContainer<usize> for OffsetOptimized {
     }
 
     fn clear(&mut self) {
-        self.spilled.clear();
         self.strided = OffsetStride::default();
+        self.spilled.clear();
     }
 
     fn len(&self) -> usize {
diff --git a/src/impls/vec.rs b/src/impls/vec.rs
new file mode 100644
index 0000000..2ab3932
--- /dev/null
+++ b/src/impls/vec.rs
@@ -0,0 +1,119 @@
+//! Region delegating to a vector.
+
+use std::ops::{Deref, DerefMut};
+use crate::{CopyOnto, Region};
+
+#[derive(Debug)]
+pub struct Vector<T>(pub Vec<T>);
+
+impl<T> Default for Vector<T> {
+    fn default() -> Self {
+        Self(Vec::default())
+    }
+}
+
+
+impl<T> Deref for Vector<T> {
+    type Target = Vec<T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T> DerefMut for Vector<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl<T: Clone> Region for Vector<T> {
+    type ReadItem<'a> = &'a T where Self: 'a;
+    type Index = usize;
+
+    fn merge_regions<'a>(regions: impl Iterator<Item=&'a Self> + Clone) -> Self where Self: 'a {
+        Self::with_capacity(regions.map(Vec::len).sum())
+    }
+
+    fn index(&self, index: Self::Index) -> Self::ReadItem<'_> {
+        &self[index]
+    }
+
+    fn reserve_regions<'a, I>(&mut self, regions: I) where Self: 'a, I: Iterator<Item=&'a Self> + Clone {
+        self.reserve(regions.map(Vec::len).sum());
+    }
+
+    fn clear(&mut self) {
+        self.clear()
+    }
+}
+
+impl<T: Clone> CopyOnto<Vector<T>> for T {
+    fn copy_onto(self, target: &mut Vector<T>) -> usize {
+        target.push(self);
+        target.len()  - 1
+    }
+}
+
+impl<T: Clone> CopyOnto<Vector<T>> for &T {
+    fn copy_onto(self, target: &mut Vector<T>) -> usize {
+        self.clone().copy_onto(target)
+    }
+}
+
+#[derive(Debug)]
+pub struct CopyVector<T>(pub Vec<T>);
+
+impl<T> Default for CopyVector<T> {
+    fn default() -> Self {
+        Self(Vec::default())
+    }
+}
+
+impl<T> Deref for CopyVector<T> {
+    type Target = Vec<T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T> DerefMut for CopyVector<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl<T: Copy> Region for CopyVector<T> {
+    type ReadItem<'a> = T where Self: 'a;
+    type Index = usize;
+
+    fn merge_regions<'a>(regions: impl Iterator<Item=&'a Self> + Clone) -> Self where Self: 'a {
+        Self::with_capacity(regions.map(Vec::len).sum())
+    }
+
+    fn index(&self, index: Self::Index) -> Self::ReadItem<'_> {
+        &self[index]
+    }
+
+    fn reserve_regions<'a, I>(&mut self, regions: I) where Self: 'a, I: Iterator<Item=&'a Self> + Clone {
+        self.reserve(regions.map(Vec::len).sum());
+    }
+
+    fn clear(&mut self) {
+        self.clear()
+    }
+}
+
+impl<T: Copy> CopyOnto<CopyVector<T>> for T {
+    fn copy_onto(self, target: &mut CopyVector<T>) -> usize {
+        target.push(self);
+        target.len()  - 1
+    }
+}
+
+impl<T: Copy> CopyOnto<CopyVector<T>> for &T {
+    fn copy_onto(self, target: &mut CopyVector<T>) -> usize {
+        self.copied().copy_onto(target)
+    }
+}