diff --git a/geant3/src/lemsr/ugeom.F b/geant3/src/lemsr/ugeom.F
index f9b757e..e550d26 100644
--- a/geant3/src/lemsr/ugeom.F
+++ b/geant3/src/lemsr/ugeom.F
@@ -441,7 +441,7 @@ c
 c       Sapphire mounted between 1. and 2. Cu plate, 0.6cm thick, 6cm diameter
 c       
         par_tube(1) = 0.
-c        par_tube(2) = 1.6
+c        par_tube(2) = 1.6      ! small sample plate
         par_tube(2) = 3.0
         par_tube(3) = 0.3
 c