diff --git a/Squirrel.xcodeproj/project.pbxproj b/Squirrel.xcodeproj/project.pbxproj
index afbe13b..a1d2e7a 100644
--- a/Squirrel.xcodeproj/project.pbxproj
+++ b/Squirrel.xcodeproj/project.pbxproj
@@ -10,6 +10,7 @@
 		5316AF7A188EFC1800C070DF /* RACSignal+SQRLFileManagerExtensions.h in Headers */ = {isa = PBXBuildFile; fileRef = 5316AF78188EFC1800C070DF /* RACSignal+SQRLFileManagerExtensions.h */; };
 		5316AF7B188EFC1800C070DF /* RACSignal+SQRLFileManagerExtensions.m in Sources */ = {isa = PBXBuildFile; fileRef = 5316AF79188EFC1800C070DF /* RACSignal+SQRLFileManagerExtensions.m */; };
 		5316AF95188EFFA100C070DF /* RACSignal+SQRLFileManagerExtensions.m in Sources */ = {isa = PBXBuildFile; fileRef = 5316AF79188EFC1800C070DF /* RACSignal+SQRLFileManagerExtensions.m */; };
+		5316AFA8188F002100C070DF /* SQRLDownload+Private.h in Headers */ = {isa = PBXBuildFile; fileRef = 5316AFA6188F002100C070DF /* SQRLDownload+Private.h */; };
 		533076EB17EB688300BDCCE0 /* IOKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = D097B9BC17BB4777006C3FEB /* IOKit.framework */; };
 		53390936184F6219009FA41F /* NSHTTPURLResponse+SQRLExtensions.h in Headers */ = {isa = PBXBuildFile; fileRef = 53390934184F6219009FA41F /* NSHTTPURLResponse+SQRLExtensions.h */; };
 		53390937184F6219009FA41F /* NSHTTPURLResponse+SQRLExtensions.m in Sources */ = {isa = PBXBuildFile; fileRef = 53390935184F6219009FA41F /* NSHTTPURLResponse+SQRLExtensions.m */; };
@@ -431,6 +432,7 @@
 /* Begin PBXFileReference section */
 		5316AF78188EFC1800C070DF /* RACSignal+SQRLFileManagerExtensions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "RACSignal+SQRLFileManagerExtensions.h"; sourceTree = "<group>"; };
 		5316AF79188EFC1800C070DF /* RACSignal+SQRLFileManagerExtensions.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "RACSignal+SQRLFileManagerExtensions.m"; sourceTree = "<group>"; };
+		5316AFA6188F002100C070DF /* SQRLDownload+Private.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "SQRLDownload+Private.h"; sourceTree = "<group>"; };
 		53390934184F6219009FA41F /* NSHTTPURLResponse+SQRLExtensions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSHTTPURLResponse+SQRLExtensions.h"; sourceTree = "<group>"; };
 		53390935184F6219009FA41F /* NSHTTPURLResponse+SQRLExtensions.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSHTTPURLResponse+SQRLExtensions.m"; sourceTree = "<group>"; };
 		53390949184F6322009FA41F /* NSHTTPURLResponseExtensionsSpec.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NSHTTPURLResponseExtensionsSpec.m; sourceTree = "<group>"; };
@@ -681,6 +683,7 @@
 				53C3186A1816C38A0074B481 /* SQRLDownloadManager.m */,
 				536CD4E0183E5D7F000C0FD1 /* SQRLDownload.h */,
 				536CD4E1183E5D7F000C0FD1 /* SQRLDownload.m */,
+				5316AFA6188F002100C070DF /* SQRLDownload+Private.h */,
 				53C3186D1816C38A0074B481 /* SQRLResumableDownload.h */,
 				53C3186E1816C38A0074B481 /* SQRLResumableDownload.m */,
 				53C3186B1816C38A0074B481 /* SQRLURLConnection.h */,
@@ -1089,6 +1092,7 @@
 				D0964B3C17F2E20B00D88BF7 /* NSBundle+SQRLVersionExtensions.h in Headers */,
 				D0C22C4C179CC15100158214 /* SQRLUpdater.h in Headers */,
 				D0C22C52179CC23900158214 /* Squirrel.h in Headers */,
+				5316AFA8188F002100C070DF /* SQRLDownload+Private.h in Headers */,
 				53390936184F6219009FA41F /* NSHTTPURLResponse+SQRLExtensions.h in Headers */,
 				D0964B3817F2E01500D88BF7 /* SQRLDownloadedUpdate.h in Headers */,
 				53AACF4B17E9CA0500B41027 /* SQRLUpdate.h in Headers */,
diff --git a/Squirrel/SQRLDownload+Private.h b/Squirrel/SQRLDownload+Private.h
new file mode 100644
index 0000000..d7f233b
--- /dev/null
+++ b/Squirrel/SQRLDownload+Private.h
@@ -0,0 +1,21 @@
+//
+//  SQRLDownload+Private.h
+//  Squirrel
+//
+//  Created by Keith Duncan on 21/01/2014.
+//  Copyright (c) 2014 GitHub. All rights reserved.
+//
+
+#import "SQRLDownload.h"
+
+@interface SQRLDownload ()
+
+// Designated initialiser.
+//
+// request - Must not be nil. The request this download is for.
+// fileURL - Must not be nil. The file location to save received data to.
+//
+// Returns an initialised download suitable for saving response data.
+- (instancetype)initWithRequest:(NSURLRequest *)request fileURL:(NSURL *)fileURL;
+
+@end
diff --git a/Squirrel/SQRLDownload.h b/Squirrel/SQRLDownload.h
index 16dea11..ba35c96 100644
--- a/Squirrel/SQRLDownload.h
+++ b/Squirrel/SQRLDownload.h
@@ -10,16 +10,13 @@
 
 @class RACSignal;
 
+// A download is a file which holds the response body for a request and can be
+// resumed by a subsequent request if the initial transfer is interrupted.
+//
+// Don't create a download directly, instead retrieve one from
+// `SQRLDownloadManager`.
 @interface SQRLDownload : MTLModel
 
-// Designated initialiser.
-//
-// request - Must not be nil. The request this download is for.
-// fileURL - Must not be nil. The file location to save received data to.
-//
-// Returns an initialised download suitable for saving response data.
-- (instancetype)initWithRequest:(NSURLRequest *)request fileURL:(NSURL *)fileURL;
-
 // The `request` the receiver was initialised with.
 @property (readonly, copy, nonatomic) NSURLRequest *request;
 
diff --git a/Squirrel/SQRLDownload.m b/Squirrel/SQRLDownload.m
index a79bc06..e72e4a8 100644
--- a/Squirrel/SQRLDownload.m
+++ b/Squirrel/SQRLDownload.m
@@ -7,6 +7,7 @@
 //
 
 #import "SQRLDownload.h"
+#import "SQRLDownload+Private.h"
 
 #import <ReactiveCocoa/ReactiveCocoa.h>
 
diff --git a/Squirrel/SQRLDownloadManager.m b/Squirrel/SQRLDownloadManager.m
index f0f89bd..1b3c48f 100644
--- a/Squirrel/SQRLDownloadManager.m
+++ b/Squirrel/SQRLDownloadManager.m
@@ -12,6 +12,8 @@
 #import <CommonCrypto/CommonCrypto.h>
 
 #import "SQRLDirectoryManager.h"
+#import "SQRLDownload.h"
+#import "SQRLDownload+Private.h"
 #import "SQRLResumableDownload.h"
 
 @interface SQRLDownloadManager ()