diff --git a/README.md b/README.md
index f2ae6da..8ce5da3 100644
--- a/README.md
+++ b/README.md
@@ -153,6 +153,10 @@ For example:
 nix-build -E "with import ./default.nix {}; nixGLCommon nixGLIntel"
 ```
 
+# Using nixGL in your project
+
+
+
 
 # Limitations
 
diff --git a/default.nix b/default.nix
index de21356..f1d544d 100644
--- a/default.nix
+++ b/default.nix
@@ -1,5 +1,4 @@
-{ system ? builtins.currentSystem,
-  ## Nvidia informations.
+{ ## Nvidia informations.
   # Version of the system kernel module. Let it to null to enable auto-detection.
   nvidiaVersion ? null,
   # Hash of the Nvidia driver .run file. null is fine, but fixing a value here
@@ -13,147 +12,8 @@
 }:
 
 let
-  # The nvidia version. Either fixed by the `nvidiaVersion` argument, or
-  # auto-detected.
-  _nvidiaVersion = if nvidiaVersion != null
-  then nvidiaVersion
-  else
-    # This is the auto-detection mecanism. This is ugly.
-    # We read /proc/driver/nvidia/version which is set by the Nvidia driver kernel module.
-    # This fails if the nvidia driver kernel module is not loaded.
-    # I'd like to just read the file using `${/proc/driver/nvidia/version}` and
-    # then let nix invalidate the derivation if the content of this file
-    # changes, but that's not possible, see
-    # https://github.com/NixOS/nix/issues/3539
-    # But /proc is readable at build time! So runCommand works fine.
-    import (nixpkgs.runCommand "auto-detect-nvidia" {
-      time = builtins.currentTime;
-      }
-      ''
-        # Written this way so if the version file does not exists, the script crashs
-        VERSION="$(${nixpkgs.pcre}/bin/pcregrep -o1 'Module +([0-9]+\.[0-9]+)' /proc/driver/nvidia/version)"
-        echo "\"$VERSION\"" > $out
-      '');
-
-  addNvidiaVersion = drv: drv.overrideAttrs(oldAttrs: {
-    name = oldAttrs.name + "-${_nvidiaVersion}";
-  });
-  
   nixpkgs = pkgs {config = {allowUnfree = true;};};
-
-  writeExecutable = { name, text } : nixpkgs.writeTextFile {
-    inherit name text;
-
-    executable = true;
-    destination = "/bin/${name}";
-
-
-    checkPhase = ''
-       ${nixpkgs.shellcheck}/bin/shellcheck "$out/bin/${name}"
-
-       # Check that all the files listed in the output binary exists
-       for i in $(${nixpkgs.pcre}/bin/pcregrep  -o0 '/nix/store/.*?/[^ ":]+' $out/bin/${name})
-       do
-         ls $i > /dev/null || (echo "File $i, referenced in $out/bin/${name} does not exists."; exit -1)
-       done
-    '';
-  };
-
 in
-with nixpkgs;
-rec {
-  nvidia = (linuxPackages.nvidia_x11.override {
-          }).overrideAttrs(oldAttrs: rec {
-            name = "nvidia-${_nvidiaVersion}";
-            src = let url ="http://download.nvidia.com/XFree86/Linux-x86_64/${_nvidiaVersion}/NVIDIA-Linux-x86_64-${_nvidiaVersion}.run";
-                  in if nvidiaHash != null
-                     then fetchurl {
-                       inherit url;
-                       sha256 = nvidiaHash;
-                     } else
-                       builtins.fetchurl url;
-            useGLVND = true;
-          });
-
-  nvidiaLibsOnly = nvidia.override {
-      libsOnly = true;
-      kernel = null;
-  };
-
-  nixGLNvidiaBumblebee = addNvidiaVersion (writeExecutable {
-    name = "nixGLNvidiaBumblebee";
-    text = ''
-      #!/usr/bin/env sh
-      export LD_LIBRARY_PATH=${lib.makeLibraryPath [nvidia]}:$LD_LIBRARY_PATH
-      ${bumblebee.override {nvidia_x11 = nvidia; nvidia_x11_i686 = nvidia.lib32;}}/bin/optirun --ldpath ${lib.makeLibraryPath ([libglvnd nvidia] ++ lib.optionals enable32bits [nvidia.lib32 pkgsi686Linux.libglvnd])} "$@"
-      '';
-  });
-
-  # TODO: 32bit version? Not tested.
-  nixNvidiaWrapper = api: addNvidiaVersion (writeExecutable {
-    name = "nix${api}Nvidia";
-    text = ''
-      #!/usr/bin/env sh
-      ${lib.optionalString (api == "Vulkan") ''export VK_LAYER_PATH=${nixpkgs.vulkan-validation-layers}/share/vulkan/explicit_layer.d''}
-
-      export LD_LIBRARY_PATH=${lib.makeLibraryPath ([
-        libglvnd
-        nvidiaLibsOnly
-      ] ++ lib.optional (api == "Vulkan") nixpkgs.vulkan-validation-layers
-      ++ lib.optionals enable32bits [nvidiaLibsOnly.lib32 pkgsi686Linux.libglvnd])
-      }:''${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
-      "$@"
-      '';
-  });
-
-  # TODO: 32bit version? Not tested.
-  nixGLNvidia = nixNvidiaWrapper "GL";
-
-  # TODO: 32bit version? Not tested.
-  nixVulkanNvidia = nixNvidiaWrapper "Vulkan";
-
-  nixGLIntel = writeExecutable {
-    name = "nixGLIntel";
-    # add the 32 bits drivers if needed
-    text = let
-      drivers = [mesa_drivers] ++ lib.optional enable32bits pkgsi686Linux.mesa_drivers;
-    in ''
-      #!/usr/bin/env sh
-      export LIBGL_DRIVERS_PATH=${lib.makeSearchPathOutput "lib" "lib/dri" drivers}
-      export LD_LIBRARY_PATH=${
-        lib.makeLibraryPath drivers
-        }:$LD_LIBRARY_PATH
-      "$@"
-      '';
-  };
-
-  # TODO: 32 bit version? Not tested.
-  nixVulkanIntel = writeExecutable {
-    name = "nixVulkanIntel";
-    text = ''
-     #!/usr/bin/env bash
-     if [ -n "$LD_LIBRARY_PATH" ]; then
-       echo "Warning, nixVulkanIntel overwriting existing LD_LIBRARY_PATH" 1>&2
-     fi
-     export LD_LIBRARY_PATH=${lib.makeLibraryPath [
-       zlib
-       libdrm
-       xorg.libX11
-       xorg.libxcb
-       xorg.libxshmfence
-       wayland
-       gcc.cc
-     ]}:$LD_LIBRARY_PATH
-     exec "$@"
-     '';
-  };
-
-  nixGLCommon = nixGL:
-    runCommand "nixGLCommon" {
-       buildInuts = [nixGL];
-    }
-    ''
-       mkdir -p "$out/bin"
-       cp "${nixGL}/bin/${nixGL.name}" "$out/bin/nixGL";
-    '';
-}
+  nixpkgs.callPackage ./nixGL.nix {
+    inherit nvidiaVersion nvidiaHash enable32bits;
+  }
diff --git a/nixGL.nix b/nixGL.nix
new file mode 100644
index 0000000..72045ef
--- /dev/null
+++ b/nixGL.nix
@@ -0,0 +1,157 @@
+{ ## Nvidia informations.
+  # Version of the system kernel module. Let it to null to enable auto-detection.
+  nvidiaVersion ? null,
+  # Hash of the Nvidia driver .run file. null is fine, but fixing a value here
+  # will be more reproducible and more efficient.
+  nvidiaHash ? null,
+  # Enable 32 bits driver
+  # This is one by default, you can switch it to off if you want to reduce a
+  # bit the size of nixGL closure.
+  enable32bits ? true,
+  writeTextFile, shellcheck, pcre, runCommand, linuxPackages, fetchurl, lib,
+  bumblebee, libglvnd, vulkan-validation-layers, mesa_drivers,
+  pkgsi686Linux,zlib, libdrm, xorg, wayland, gcc
+}:
+
+let
+  # The nvidia version. Either fixed by the `nvidiaVersion` argument, or
+  # auto-detected.
+  _nvidiaVersion = if nvidiaVersion != null
+  then nvidiaVersion
+  else
+    # This is the auto-detection mecanism. This is ugly.
+    # We read /proc/driver/nvidia/version which is set by the Nvidia driver kernel module.
+    # This fails if the nvidia driver kernel module is not loaded.
+    # I'd like to just read the file using `${/proc/driver/nvidia/version}` and
+    # then let nix invalidate the derivation if the content of this file
+    # changes, but that's not possible, see
+    # https://github.com/NixOS/nix/issues/3539
+    # But /proc is readable at build time! So runCommand works fine.
+    import (runCommand "auto-detect-nvidia" {
+      time = builtins.currentTime;
+    }
+    ''
+        # Written this way so if the version file does not exists, the script crashs
+        VERSION="$(${pcre}/bin/pcregrep -o1 'Module +([0-9]+\.[0-9]+)' /proc/driver/nvidia/version)"
+        echo "\"$VERSION\"" > $out
+    '');
+
+    addNvidiaVersion = drv: drv.overrideAttrs(oldAttrs: {
+      name = oldAttrs.name + "-${_nvidiaVersion}";
+    });
+
+    writeExecutable = { name, text } : writeTextFile {
+      inherit name text;
+
+      executable = true;
+      destination = "/bin/${name}";
+
+
+      checkPhase = ''
+       ${shellcheck}/bin/shellcheck "$out/bin/${name}"
+
+       # Check that all the files listed in the output binary exists
+       for i in $(${pcre}/bin/pcregrep  -o0 '/nix/store/.*?/[^ ":]+' $out/bin/${name})
+       do
+         ls $i > /dev/null || (echo "File $i, referenced in $out/bin/${name} does not exists."; exit -1)
+       done
+      '';
+    };
+
+in
+  rec {
+    nvidia = (linuxPackages.nvidia_x11.override {
+    }).overrideAttrs(oldAttrs: rec {
+      name = "nvidia-${_nvidiaVersion}";
+      src = let url ="http://download.nvidia.com/XFree86/Linux-x86_64/${_nvidiaVersion}/NVIDIA-Linux-x86_64-${_nvidiaVersion}.run";
+      in if nvidiaHash != null
+      then fetchurl {
+        inherit url;
+        sha256 = nvidiaHash;
+      } else
+      builtins.fetchurl url;
+      useGLVND = true;
+    });
+
+    nvidiaLibsOnly = nvidia.override {
+      libsOnly = true;
+      kernel = null;
+    };
+
+  nixGLNvidiaBumblebee = addNvidiaVersion (writeExecutable {
+    name = "nixGLNvidiaBumblebee";
+    text = ''
+      #!/usr/bin/env sh
+      export LD_LIBRARY_PATH=${lib.makeLibraryPath [nvidia]}:$LD_LIBRARY_PATH
+      ${bumblebee.override {nvidia_x11 = nvidia; nvidia_x11_i686 = nvidia.lib32;}}/bin/optirun --ldpath ${lib.makeLibraryPath ([libglvnd nvidia] ++ lib.optionals enable32bits [nvidia.lib32 pkgsi686Linux.libglvnd])} "$@"
+    '';
+  });
+
+  # TODO: 32bit version? Not tested.
+  nixNvidiaWrapper = api: addNvidiaVersion (writeExecutable {
+    name = "nix${api}Nvidia";
+    text = ''
+      #!/usr/bin/env sh
+      ${lib.optionalString (api == "Vulkan") ''export VK_LAYER_PATH=${vulkan-validation-layers}/share/vulkan/explicit_layer.d''}
+
+        export LD_LIBRARY_PATH=${lib.makeLibraryPath ([
+          libglvnd
+          nvidiaLibsOnly
+        ] ++ lib.optional (api == "Vulkan") vulkan-validation-layers
+        ++ lib.optionals enable32bits [nvidia.lib32 pkgsi686Linux.libglvnd])
+      }:''${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
+        "$@"
+      '';
+    });
+
+  # TODO: 32bit version? Not tested.
+  nixGLNvidia = nixNvidiaWrapper "GL";
+
+  # TODO: 32bit version? Not tested.
+  nixVulkanNvidia = nixNvidiaWrapper "Vulkan";
+
+  nixGLIntel = writeExecutable {
+    name = "nixGLIntel";
+    # add the 32 bits drivers if needed
+    text = let
+      drivers = [mesa_drivers] ++ lib.optional enable32bits pkgsi686Linux.mesa_drivers;
+    in ''
+      #!/usr/bin/env sh
+      export LIBGL_DRIVERS_PATH=${lib.makeSearchPathOutput "lib" "lib/dri" drivers}
+      export LD_LIBRARY_PATH=${
+        lib.makeLibraryPath drivers
+      }:$LD_LIBRARY_PATH
+      "$@"
+    '';
+  };
+
+  # TODO: 32 bit version? Not tested.
+  nixVulkanIntel = writeExecutable {
+    name = "nixVulkanIntel";
+    text = ''
+     #!/usr/bin/env bash
+     if [ -n "$LD_LIBRARY_PATH" ]; then
+       echo "Warning, nixVulkanIntel overwriting existing LD_LIBRARY_PATH" 1>&2
+     fi
+     export LD_LIBRARY_PATH=${lib.makeLibraryPath [
+       zlib
+       libdrm
+       xorg.libX11
+       xorg.libxcb
+       xorg.libxshmfence
+       wayland
+       gcc.cc
+     ]}:$LD_LIBRARY_PATH
+     exec "$@"
+    '';
+  };
+
+  nixGLCommon = nixGL:
+  runCommand "nixGLCommon" {
+  buildInuts = [nixGL];
+  }
+  ''
+  mkdir -p "$out/bin"
+  cp "${nixGL}/bin/${nixGL.name}" "$out/bin/nixGL";
+  '';
+  }