diff --git a/README.md b/README.md
index d96f153..68440a9 100644
--- a/README.md
+++ b/README.md
@@ -10,6 +10,9 @@ tar-stream is a streaming tar parser and generator and nothing else. It is strea
 
 tar-stream exposes two streams, [pack](https://github.com/mafintosh/tar-stream#packing) which creates tarballs and [extract](https://github.com/mafintosh/tar-stream#extracting) which extracts tarballs. To [modify an existing tarball](https://github.com/mafintosh/tar-stream#modifying-existing-tarballs) use both.
 
+
+It implementes USTAR with additional support for pax extended headers. It should be compatible with all popular tar distributions out there (gnutar, bsdtar etc)
+
 ## Related
 
 If you want to pack/unpack directories on the file system check out [tar-fs](https://github.com/mafintosh/tar-fs) which provides file system bindings to this module.