diff --git a/src/ring_extrude.scad b/src/ring_extrude.scad
index b60f5b68..ee684b54 100644
--- a/src/ring_extrude.scad
+++ b/src/ring_extrude.scad
@@ -1,3 +1,16 @@
+/**
+* ring_extrude.scad
+*
+* Rotational extrusion spins a 2D shape around the Z-axis.  
+* It's similar to the built-in `rotate_extrude`; however, it supports angle, twist and scale options.
+*
+* @copyright Justin Lin, 2017
+* @license https://opensource.org/licenses/lgpl-3.0.html
+*
+* @see https://openhome.cc/eGossip/OpenSCAD/lib-ring_extrude.html
+*
+**/
+
 module ring_extrude(shape_pts, radius, angle = 360, twist = 0, scale = 1.0, triangles = "RADIAL") {
     frags = $fn > 0 ? 
             ($fn >= 3 ? $fn : 3) :