diff --git a/CHANGELOG.md b/CHANGELOG.md
index 296107a18..c61bcb6c0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,17 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/).
 
 ## [Unreleased]
+### Added
+- `IterableLens#mapping`, an `Iso` that maps values
+
+### Changed
+- `TypeSafeKey.Simple` now has a default `#apply` implementation
+
+### Fixed
+- mapped `TypeSafeKey` instances can be used for initial put in an `HMap`, and the base key can be used to retrieve them
+- Merged pull request fixing issue storing values at mapped `TypeSafeKey` in `singletonHMap` 
+
+## [3.0.1] - 2018-05-13
 ### Changed
 - `ToMap` accepts an `Iterable` covariant in `Map.Entry`
 - `RecursiveResult#invert` is also a `RecursiveResult`
@@ -312,7 +323,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/).
 - `Monadic/Dyadic/TriadicFunction`, `Predicate`, `Tuple2`, `Tuple3`
 - `Functor`, `BiFunctor`, `ProFunctor` 
 
-[Unreleased]: https://github.com/palatable/lambda/compare/lambda-3.0.0...HEAD
+[Unreleased]: https://github.com/palatable/lambda/compare/lambda-3.0.1...HEAD
+[3.0.1]: https://github.com/palatable/lambda/compare/lambda-3.0.0...lambda-3.0.1
 [3.0.0]: https://github.com/palatable/lambda/compare/lambda-2.1.1...lambda-3.0.0
 [2.1.1]: https://github.com/palatable/lambda/compare/lambda-2.1.0...lambda-2.1.1
 [2.1.0]: https://github.com/palatable/lambda/compare/lambda-2.0.0...lambda-2.1.0
diff --git a/README.md b/README.md
index 5d8eff2e7..a08d8dcc8 100644
--- a/README.md
+++ b/README.md
@@ -57,14 +57,14 @@ Add the following dependency to your:
 <dependency>
     <groupId>com.jnape.palatable</groupId>
     <artifactId>lambda</artifactId>
-    <version>3.0.0</version>
+    <version>3.0.1</version>
 </dependency>
 ```
 
 `build.gradle` ([Gradle](https://docs.gradle.org/current/userguide/dependency_management.html)):
 
 ```gradle
-compile group: 'com.jnape.palatable', name: 'lambda', version: '3.0.0'
+compile group: 'com.jnape.palatable', name: 'lambda', version: '3.0.1'
 ```
 
 <a name="examples">Examples</a>
diff --git a/pom.xml b/pom.xml
index 21483d5fe..ac48a3a91 100644
--- a/pom.xml
+++ b/pom.xml
@@ -9,7 +9,7 @@
     </parent>
 
     <artifactId>lambda</artifactId>
-    <version>3.0.1</version>
+    <version>3.0.2</version>
     <packaging>jar</packaging>
 
     <name>Lambda</name>
diff --git a/src/main/java/com/jnape/palatable/lambda/adt/hmap/HMap.java b/src/main/java/com/jnape/palatable/lambda/adt/hmap/HMap.java
index 83fc47f11..e2e3fd3c1 100644
--- a/src/main/java/com/jnape/palatable/lambda/adt/hmap/HMap.java
+++ b/src/main/java/com/jnape/palatable/lambda/adt/hmap/HMap.java
@@ -196,7 +196,7 @@ public static HMap emptyHMap() {
      * @return a singleton HMap
      */
     public static <V> HMap singletonHMap(TypeSafeKey<?, V> key, V value) {
-        return new HMap(singletonMap(key, value));
+        return emptyHMap().put(key, value);
     }
 
     /**
diff --git a/src/main/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKey.java b/src/main/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKey.java
index a71e4c04c..8bae70949 100644
--- a/src/main/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKey.java
+++ b/src/main/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKey.java
@@ -6,6 +6,8 @@
 import com.jnape.palatable.lambda.lens.Iso;
 import com.jnape.palatable.lambda.lens.LensLike;
 
+import java.util.Objects;
+
 /**
  * An interface representing a parametrized key for use in {@link HMap}s. Additionally, every {@link TypeSafeKey} is an
  * {@link Iso} from the type the value is stored as to the type it's viewed and set as (on the way in / on the way out).
@@ -88,10 +90,8 @@ public boolean equals(Object obj) {
     static <A> Simple<A> typeSafeKey() {
         return new TypeSafeKey.Simple<A>() {
             @Override
-            @SuppressWarnings("unchecked")
-            public <P extends Profunctor, F extends Functor, FB extends Functor<A, F>, FT extends Functor<A, F>, PAFB extends Profunctor<A, FB, P>, PSFT extends Profunctor<A, FT, P>> PSFT apply(
-                    PAFB pafb) {
-                return (PSFT) pafb;
+            public boolean equals(Object obj) {
+                return obj instanceof Simple ? this == obj : Objects.equals(obj, this);
             }
         };
     }
@@ -102,5 +102,12 @@ public <P extends Profunctor, F extends Functor, FB extends Functor<A, F>, FT ex
      * @param <A> The type of the value that this key maps to inside an {@link HMap}
      */
     interface Simple<A> extends TypeSafeKey<A, A> {
+
+        @Override
+        @SuppressWarnings("unchecked")
+        default <P extends Profunctor, F extends Functor, FB extends Functor<A, F>, FT extends Functor<A, F>, PAFB extends Profunctor<A, FB, P>, PSFT extends Profunctor<A, FT, P>> PSFT apply(
+                PAFB pafb) {
+            return (PSFT) pafb;
+        }
     }
 }
\ No newline at end of file
diff --git a/src/main/java/com/jnape/palatable/lambda/lens/lenses/IterableLens.java b/src/main/java/com/jnape/palatable/lambda/lens/lenses/IterableLens.java
index 0c765505d..cccf68730 100644
--- a/src/main/java/com/jnape/palatable/lambda/lens/lenses/IterableLens.java
+++ b/src/main/java/com/jnape/palatable/lambda/lens/lenses/IterableLens.java
@@ -3,12 +3,16 @@
 import com.jnape.palatable.lambda.adt.Maybe;
 import com.jnape.palatable.lambda.functions.builtin.fn1.Head;
 import com.jnape.palatable.lambda.functions.builtin.fn1.Tail;
+import com.jnape.palatable.lambda.lens.Iso;
 import com.jnape.palatable.lambda.lens.Lens;
 
 import static com.jnape.palatable.lambda.functions.Fn2.fn2;
 import static com.jnape.palatable.lambda.functions.builtin.fn1.Id.id;
 import static com.jnape.palatable.lambda.functions.builtin.fn2.Cons.cons;
+import static com.jnape.palatable.lambda.functions.builtin.fn2.Map.map;
+import static com.jnape.palatable.lambda.lens.Iso.simpleIso;
 import static com.jnape.palatable.lambda.lens.Lens.simpleLens;
+import static com.jnape.palatable.lambda.lens.functions.View.view;
 
 /**
  * Lenses that operate on {@link Iterable}s.
@@ -43,4 +47,16 @@ public static <A> Lens.Simple<Iterable<A>, Maybe<A>> head() {
     public static <A> Lens.Simple<Iterable<A>, Iterable<A>> tail() {
         return simpleLens(Tail::tail, fn2(Head.<A>head().andThen(o -> o.fmap(cons()).orElse(id()))).toBiFunction());
     }
+
+    /**
+     * An iso focusing on the mapped values of an {@link Iterable}.
+     *
+     * @param abIso the iso from A to B
+     * @param <A>   the unmapped {@link Iterable} element type
+     * @param <B>   the mapped {@link Iterable} element type
+     * @return an iso that maps {@link Iterable}&lt;A&gt; to {@link Iterable}&lt;B&gt;
+     */
+    public static <A, B> Iso.Simple<Iterable<A>, Iterable<B>> mapping(Iso<A, A, B, B> abIso) {
+        return simpleIso(map(view(abIso)), map(view(abIso.mirror())));
+    }
 }
diff --git a/src/test/java/com/jnape/palatable/lambda/adt/hmap/HMapTest.java b/src/test/java/com/jnape/palatable/lambda/adt/hmap/HMapTest.java
index 8495b059f..65db8ee50 100644
--- a/src/test/java/com/jnape/palatable/lambda/adt/hmap/HMapTest.java
+++ b/src/test/java/com/jnape/palatable/lambda/adt/hmap/HMapTest.java
@@ -2,6 +2,7 @@
 
 import org.junit.Test;
 
+import java.math.BigInteger;
 import java.util.HashMap;
 import java.util.NoSuchElementException;
 
@@ -12,6 +13,8 @@
 import static com.jnape.palatable.lambda.adt.hmap.HMap.hMap;
 import static com.jnape.palatable.lambda.adt.hmap.HMap.singletonHMap;
 import static com.jnape.palatable.lambda.adt.hmap.TypeSafeKey.typeSafeKey;
+import static com.jnape.palatable.lambda.lens.Iso.simpleIso;
+import static java.math.BigInteger.ONE;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotEquals;
@@ -36,6 +39,28 @@ public void getForAbsentKey() {
                              .get(typeSafeKey()));
     }
 
+    @Test
+    public void storesTypeSafeKeyBaseValue() {
+        TypeSafeKey.Simple<String> stringKey = typeSafeKey();
+        TypeSafeKey<String, Long> longKey = stringKey.andThen(simpleIso(Long::parseLong, String::valueOf));
+        TypeSafeKey<String, BigInteger> bigIntegerKey = longKey.andThen(simpleIso(BigInteger::valueOf, BigInteger::longValue));
+
+        HMap hMap = singletonHMap(stringKey, "1");
+        assertEquals(just("1"), hMap.get(stringKey));
+        assertEquals(just(1L), hMap.get(longKey));
+        assertEquals(just(ONE), hMap.get(bigIntegerKey));
+
+        assertNotEquals(typeSafeKey(), typeSafeKey());
+
+        assertEquals(emptyHMap().put(longKey, 1L).get(longKey), emptyHMap().put(stringKey, "1").get(longKey));
+        assertEquals(emptyHMap().put(stringKey, "1").get(stringKey), emptyHMap().put(longKey, 1L).get(stringKey));
+        assertEquals(emptyHMap().put(stringKey, "1").get(stringKey), emptyHMap().put(bigIntegerKey, ONE).get(stringKey));
+
+        assertEquals(singletonHMap(stringKey, "1"), singletonHMap(longKey, 1L));
+        assertEquals(singletonHMap(stringKey, "1"), singletonHMap(bigIntegerKey, ONE));
+        assertEquals(singletonHMap(longKey, 1L), singletonHMap(bigIntegerKey, ONE));
+    }
+
     @Test
     public void getForPresentKeyWithNullValue() {
         TypeSafeKey<String, String> stringKey = typeSafeKey();
diff --git a/src/test/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKeyTest.java b/src/test/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKeyTest.java
index 577902c8c..b9bb7e802 100644
--- a/src/test/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKeyTest.java
+++ b/src/test/java/com/jnape/palatable/lambda/adt/hmap/TypeSafeKeyTest.java
@@ -9,6 +9,7 @@
 import static com.jnape.palatable.lambda.lens.Iso.simpleIso;
 import static java.util.Arrays.asList;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
 import static testsupport.assertion.LensAssert.assertLensLawfulness;
 
 
@@ -45,4 +46,29 @@ public void discardRPreservesTypeSafeKey() {
 
         assertEquals(just("123"), map.get(discardedKey));
     }
+
+    @Test
+    public void defaultEquality() {
+        TypeSafeKey.Simple<Object> keyA = typeSafeKey();
+        TypeSafeKey<Object, Object> mappedKeyA = keyA.andThen(simpleIso(id(), id()));
+
+        assertEquals(keyA, keyA);
+        assertEquals(keyA, mappedKeyA);
+        assertEquals(mappedKeyA, keyA);
+        assertEquals(keyA.hashCode(), mappedKeyA.hashCode());
+
+        TypeSafeKey.Simple<Object> keyB = typeSafeKey();
+        assertNotEquals(keyA, keyB);
+        assertNotEquals(keyB, keyA);
+        assertNotEquals(keyB, mappedKeyA);
+        assertNotEquals(mappedKeyA, keyB);
+
+        TypeSafeKey<Object, Object> differentMappedKeyA = keyA.andThen(simpleIso(id(), id()));
+        assertEquals(keyA, differentMappedKeyA);
+        assertEquals(differentMappedKeyA, keyA);
+        assertEquals(mappedKeyA, differentMappedKeyA);
+        assertEquals(differentMappedKeyA, mappedKeyA);
+        assertEquals(keyA.hashCode(), differentMappedKeyA.hashCode());
+        assertEquals(mappedKeyA.hashCode(), differentMappedKeyA.hashCode());
+    }
 }
\ No newline at end of file
diff --git a/src/test/java/com/jnape/palatable/lambda/lens/lenses/IterableLensTest.java b/src/test/java/com/jnape/palatable/lambda/lens/lenses/IterableLensTest.java
index ff5e30327..561bc4d99 100644
--- a/src/test/java/com/jnape/palatable/lambda/lens/lenses/IterableLensTest.java
+++ b/src/test/java/com/jnape/palatable/lambda/lens/lenses/IterableLensTest.java
@@ -1,12 +1,14 @@
 package com.jnape.palatable.lambda.lens.lenses;
 
 import com.jnape.palatable.lambda.adt.Maybe;
+import com.jnape.palatable.lambda.lens.Iso;
 import com.jnape.palatable.lambda.lens.Lens;
 import org.junit.Test;
 
 import static com.jnape.palatable.lambda.adt.Maybe.just;
 import static com.jnape.palatable.lambda.adt.Maybe.nothing;
 import static com.jnape.palatable.lambda.functions.builtin.fn2.Map.map;
+import static com.jnape.palatable.lambda.lens.Iso.simpleIso;
 import static com.jnape.palatable.lambda.lens.functions.Over.over;
 import static com.jnape.palatable.lambda.lens.functions.Set.set;
 import static com.jnape.palatable.lambda.lens.functions.View.view;
@@ -51,4 +53,19 @@ public void tail() {
         assertThat(over(tail, map(x -> x + 1), emptyList()), isEmpty());
         assertThat(over(tail, map(x -> x + 1), asList(1, 2, 3)), iterates(1, 3, 4));
     }
+
+    @Test
+    public void mapping() {
+        Iso.Simple<Iterable<String>, Iterable<Integer>> iso = IterableLens.mapping(simpleIso(Integer::parseInt, Object::toString));
+
+        assertThat(view(iso, emptyList()), isEmpty());
+        assertThat(view(iso, singletonList("1")), iterates(1));
+        assertThat(view(iso, asList("1", "2", "3")), iterates(1, 2, 3));
+
+        assertThat(set(iso, emptyList(), emptyList()), isEmpty());
+        assertThat(set(iso, singletonList(1), emptyList()), iterates("1"));
+        assertThat(set(iso, singletonList(2), singletonList("1")), iterates("2"));
+        assertThat(set(iso, asList(1, 2, 3), singletonList("1")), iterates("1", "2", "3"));
+        assertThat(set(iso, emptyList(), singletonList("1")), isEmpty());
+    }
 }
\ No newline at end of file