diff --git a/docs/hazmat/backends/interfaces.rst b/docs/hazmat/backends/interfaces.rst
index 49e4c88..5131ca1 100644
--- a/docs/hazmat/backends/interfaces.rst
+++ b/docs/hazmat/backends/interfaces.rst
@@ -19,6 +19,11 @@
     A backend which provides methods for using ciphers for encryption
     and decryption.
 
+    The following backends implement this interface:
+
+    * :doc:`/hazmat/backends/openssl`
+    * :doc:`/hazmat/backends/commoncrypto`
+
     .. method:: cipher_supported(cipher, mode)
 
         Check if a ``cipher`` and ``mode`` combination is supported by
@@ -76,6 +81,11 @@
 
     A backend with methods for using cryptographic hash functions.
 
+    The following backends implement this interface:
+
+    * :doc:`/hazmat/backends/openssl`
+    * :doc:`/hazmat/backends/commoncrypto`
+
     .. method:: hash_supported(algorithm)
 
         Check if the specified ``algorithm`` is supported by this backend.
@@ -107,6 +117,11 @@
     A backend with methods for using cryptographic hash functions as message
     authentication codes.
 
+    The following backends implement this interface:
+
+    * :doc:`/hazmat/backends/openssl`
+    * :doc:`/hazmat/backends/commoncrypto`
+
     .. method:: hmac_supported(algorithm)
 
         Check if the specified ``algorithm`` is supported by this backend.
@@ -139,6 +154,11 @@
 
     A backend with methods for using PBKDF2 using HMAC as a PRF.
 
+    The following backends implement this interface:
+
+    * :doc:`/hazmat/backends/openssl`
+    * :doc:`/hazmat/backends/commoncrypto`
+
     .. method:: pbkdf2_hmac_supported(algorithm)
 
         Check if the specified ``algorithm`` is supported by this backend.
@@ -171,4 +191,3 @@
             the derived key. This is typically a password.
 
         :return bytes: Derived key.
-
diff --git a/docs/hazmat/primitives/constant-time.rst b/docs/hazmat/primitives/constant-time.rst
index 632e7c6..c6fcb3a 100644
--- a/docs/hazmat/primitives/constant-time.rst
+++ b/docs/hazmat/primitives/constant-time.rst
@@ -19,8 +19,10 @@
 
 .. function:: bytes_eq(a, b)
 
-    Compare ``a`` and ``b`` to one another in constant time if they are of the
-    same length.
+    Compares ``a`` and ``b`` with one another. If ``a`` and ``b`` have
+    different lengths, this returns ``False`` immediately. Otherwise it
+    compares them in a way that takes the same amount of time, regardless of
+    how many characters are the same between the two.
 
     .. doctest::
 
@@ -30,9 +32,10 @@
         >>> constant_time.bytes_eq(b"foo", b"bar")
         False
 
-    :param a bytes: The left-hand side.
-    :param b bytes: The right-hand side.
-    :returns boolean: True if ``a`` has the same bytes as ``b``.
+    :param bytes a: The left-hand side.
+    :param bytes b: The right-hand side.
+    :returns bool: ``True`` if ``a`` has the same bytes as ``b``, otherwise
+                   ``False``.
 
 
 .. _`Coda Hale's blog post`: http://codahale.com/a-lesson-in-timing-attacks/