diff --git a/gds/elements.py b/gds/elements.py
index 9665b7a..ab65758 100644
--- a/gds/elements.py
+++ b/gds/elements.py
@@ -64,13 +64,12 @@ class Box(Element, Drawable):
     points = []
 
 class SRef(Element):
-    Position = None
-    Structure = ""
+    position = (0,0)
+    structure = ""
     
     transformation  = Transformation()
 
     # tree
-    Parent   = None
-    Children = []
+    parent   = None