diff --git a/src/filters/rclrar b/src/filters/rclrar
index d4fcd2b7..e6b38bb1 100755
--- a/src/filters/rclrar
+++ b/src/filters/rclrar
@@ -24,12 +24,24 @@ import sys
 import rclexecm
 import os
 
-# We can use two different unrar python modules. Either python-rarfile
-# which is a wrapper over the the unrar command line, or python-unrar
-# which is a ctypes wrapper of the unrar lib. Python-rarfile is the
-# one commonly packaged on linux. Their interfaces is similar. Note
-# that python-unrar uses forward slashes in internal file paths while
-# python-rarfile uses backslashes (ipaths are opaque anyway).
+# We can use two different unrar python modules. Either python3-rarfile
+# which is a wrapper over the the unrar command line, or python3-unrar
+# which is a ctypes wrapper of the unrar lib.
+#
+# Python3-rarfile is the one commonly packaged on linux.
+#
+# Python3-unrar needs the libunrar library, built from unrar source
+# code (https://www.rarlab.com/rar_add.htm), which is not packaged on
+# Debian or Fedora, probably because of licensing issues. It is
+# packaged as libunrar5 on Ubuntu, and there are Fedora packages on
+# RPM Fusion, and it's probably easy to build the Ubuntu package on
+# Debian.  Python-unrar works much better and is the right choice if
+# the licensing is not an issue.
+#
+# The interfaces is similar, but python-unrar uses forward slashes
+# in internal file paths while python-rarfile uses backslashes (ipaths
+# are opaque anyway).
+
 using_unrar = False
 try:
     from unrar import rarfile