diff --git a/packages/effect-fc/src/Lens.ts b/packages/effect-fc/src/Lens.ts
index 14eecbd..50b46d7 100644
--- a/packages/effect-fc/src/Lens.ts
+++ b/packages/effect-fc/src/Lens.ts
@@ -1,4 +1,5 @@
-import { Chunk, Effect, Function, Pipeable, Predicate, Readable, Stream, Subscribable, SubscriptionRef } from "effect"
+import { Array, Chunk, Effect, Function, Pipeable, Predicate, Readable, Stream, Subscribable, SubscriptionRef } from "effect"
+import type { NoSuchElementException } from "effect/Cause"
 
 
 export const LensTypeId: unique symbol = Symbol.for("@effect-fc/Lens/Lens")
@@ -136,6 +137,60 @@ export const mapEffect: {
     )),
 }))
 
+export const mapArrayAt: {
+    <A, ER, EW, RR, RW>(
+        self: Lens<readonly A[], ER, EW, RR, RW>,
+        index: number,
+    ): Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
+    <A, ER, EW, RR, RW>(
+        index: number
+    ): (self: Lens<readonly A[], ER, EW, RR, RW>) => Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
+} = Function.dual(2, <A, ER, EW, RR, RW>(
+    self: Lens<readonly A[], ER, EW, RR, RW>,
+    index: number,
+): Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW> => mapEffect(
+    self,
+    Array.get(index),
+    (a, b) => Array.replaceOption(a, index, b)),
+)
+
+export const mapMutableArrayAt: {
+    <A, ER, EW, RR, RW>(
+        self: Lens<A[], ER, EW, RR, RW>,
+        index: number,
+    ): Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
+    <A, ER, EW, RR, RW>(
+        index: number
+    ): (self: Lens<A[], ER, EW, RR, RW>) => Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW>
+} = Function.dual(2, <A, ER, EW, RR, RW>(
+    self: Lens<A[], ER, EW, RR, RW>,
+    index: number,
+): Lens<A, ER | NoSuchElementException, EW | NoSuchElementException, RR, RW> => mapEffect(
+    self,
+    Array.get(index),
+    (a, b) => Effect.flatMap(
+        Array.get(a, index),
+        () => Effect.as(Effect.sync(() => { a[index] = b }), a),
+    ),
+))
+
+export const mapChunkAt: {
+    <A, ER, EW, RR, RW>(
+        self: Lens<Chunk.Chunk<A>, ER, EW, RR, RW>,
+        index: number,
+    ): Lens<A, ER | NoSuchElementException, EW, RR, RW>
+    <A, ER, EW, RR, RW>(
+        index: number
+    ): (self: Lens<Chunk.Chunk<A>, ER, EW, RR, RW>) => Lens<A, ER | NoSuchElementException, EW, RR, RW>
+} = Function.dual(2, <A, ER, EW, RR, RW>(
+    self: Lens<Chunk.Chunk<A>, ER, EW, RR, RW>,
+    index: number,
+): Lens<A, ER | NoSuchElementException, EW, RR, RW> => mapEffect(
+    self,
+    Chunk.get(index),
+    (a, b) => Effect.succeed(Chunk.replace(a, index, b))),
+)
+
 
 export const get = <A, ER, EW, RR, RW>(self: Lens<A, ER, EW, RR, RW>): Effect.Effect<A, ER, RR> => self.get
 
@@ -219,7 +274,7 @@ Effect.gen(function*() {
     const myChunkRef = yield* SubscriptionRef.make(Chunk.make(12, 38, 69) as Chunk.Chunk<number>)
     const chunkValueLens = myChunkRef.pipe(
         fromSubscriptionRef,
-        mapEffect(Chunk.get(1), (a, b) => Effect.succeed(Chunk.replace(a, 1, b)))
+        mapChunkAt(1),
     )
 
     console.log(yield* myChunkRef.get, yield* chunkValueLens.get)