diff --git a/lib/TileMasker.js b/lib/TileMasker.js
index c577ef5..420b258 100644
--- a/lib/TileMasker.js
+++ b/lib/TileMasker.js
@@ -214,6 +214,19 @@ ltjs.TileMasker = Class( 'TileMasker',
     },
 
 
+    /**
+     * For use by subtypes that may need access to the otherwise private data
+     *
+     * See getMaskedTileSet().
+     *
+     * @return  {Array.<number>}  tile width, height and number per row
+     */
+    'protected getTileDimensions': function()
+    {
+        return [ this._tileWidth, this._tileHeight, this._tilesPerRow ];
+    },
+
+
     /**
      * Apply mask to each tile and return individual tiles
      *