diff --git a/README.md b/README.md
index 02e0acc..1716a3e 100644
--- a/README.md
+++ b/README.md
@@ -11,8 +11,10 @@ The flake outputs are documented in `flake.nix` but an overview:
 
   * Default package and "app" is the latest released version
   * `packages.<version>` for a tagged release
-  * `packages.master.<date>` for a nightly release
-  * `packages.master.latest` for the latest nightly release
+  * `packages.master` for the latest nightly release
+  * `packages.master-<date>` for a nightly release
+  * `overlay` is an overlay that adds `zigpkgs` to be the packages
+    exposed by this flake
 
 ## Usage
 
@@ -35,10 +37,10 @@ In a shell:
 ```sh
 # run the latest released version
 $ nix run 'github:mitchellh/zig-overlay'
-# open a shell with master version dated 2021-02-13 (oldest version available)
-$ nix shell 'github:mitchellh/zig-overlay#master."2021-02-13"'
-# open a shell with latest master version
-$ nix shell 'github:mitchellh/zig-overlay#master.latest'
+# open a shell with nightly version dated 2021-02-13 (oldest version available)
+$ nix shell 'github:mitchellh/zig-overlay#master-2021-02-13'
+# open a shell with latest nightly version
+$ nix shell 'github:mitchellh/zig-overlay#master'
 ```
 
 ## Thanks
diff --git a/default.nix b/default.nix
index 9d5a3cf..a94f16a 100644
--- a/default.nix
+++ b/default.nix
@@ -23,25 +23,26 @@ let
     '';
   };
 
+  # The packages that are tagged releases
+  taggedPackages = lib.attrsets.mapAttrs
+    (k: v: mkBinaryInstall { inherit (v.${system}) version url sha256; })
+    (builtins.removeAttrs sources ["master"]);
+
+  # The master packages
+  masterPackages = lib.attrsets.mapAttrs'
+    (k: v: lib.attrsets.nameValuePair
+      (if k == "latest" then "master" else ("master-" + k))
+      (mkBinaryInstall { inherit (v.${system}) version url sha256; })
+    )
+    sources.master;
+
   # This determines the latest /released/ version.
   latest = lib.lists.last (
     builtins.sort
       (x: y: (builtins.compareVersions x y) < 0)
-      (builtins.filter (x: x != "master") (builtins.attrNames sources))
+      (builtins.attrNames taggedPackages)
   );
-
-  # This is the full list of packages
-  packages = lib.attrsets.mapAttrs (k: v:
-    if k == "master" then
-      lib.attrsets.mapAttrs (k: v: (mkBinaryInstall {
-        inherit (v.${system}) version url sha256;
-      })) v
-    else
-      mkBinaryInstall {
-        inherit (v.${system}) version url sha256;
-      })
-      sources;
 in
   # We want the packages but also add a "default" that just points to the
   # latest released version.
-  packages // { "default" = packages.${latest}; }
+  taggedPackages // masterPackages // { "default" = taggedPackages.${latest}; }
diff --git a/flake.nix b/flake.nix
index 1690d42..b0e9192 100644
--- a/flake.nix
+++ b/flake.nix
@@ -13,10 +13,24 @@
     in flake-utils.lib.eachSystem systems (system:
       let pkgs = nixpkgs.legacyPackages.${system};
       in rec {
+        # The packages exported by the Flake:
+        #  - default - latest /released/ version
+        #  - <version> - tagged version
+        #  - master - latest nightly (updated daily)
+        #  - master-<date> - nightly by date
         packages = import ./default.nix { inherit system pkgs; };
+
+        # "Apps" so that `nix run` works. If you run `nix run .` then
+        # this will use the latest default.
         apps = rec {
           default = apps.zig;
           zig = flake-utils.lib.mkApp { drv = packages.default; };
         };
+
+        # Overlay that can be imported so you can access the packages
+        # using zigpkgs.master.latest or whatever you'd like.
+        overlay = final: prev: {
+          zigpkgs = packages.${prev.system};
+        };
       });
 }