diff --git a/SlidingSurface3D/rfpm.geo b/SlidingSurface3D/rfpm.geo
index abad140d0e2f87e09521748251e9629236308a01..83c769132d7137b3e4d091055ebb9728e3a90972 100644
--- a/SlidingSurface3D/rfpm.geo
+++ b/SlidingSurface3D/rfpm.geo
@@ -9,20 +9,44 @@ tol = 1e-6;
 AnglePole = (ModelAngleMax - ModelAngleMin) * deg;
 AngleMagnet = 0.8 * AnglePole;
 
-// radial dimensions
-lRotor = 44 * mm;
-lMagnetIn = 10 * mm;
-lMagnetOut = 5 * mm;
-lGapRotor = 7 * mm;
-lGapStator = 3 * mm;
-lAirRing = 1 * mm;
-lStator = 30 * mm;
-lInf = 30 * mm;
-
-// heights
-hRotor = 80 * mm;
-hMagnet = 40 * mm;
-hTot = 130 * mm;
+DefineConstant[
+  // radial dimensions
+  lRotor = {44, Range{1,100}, Step 1,
+    Name "}Dimensions/Rotor/Radius [mm]"}
+  lMagnetIn = {10, Range{0,100}, Step 1,
+    Name "}Dimensions/Magnet/In-rotor thickness [mm]"}
+  lMagnetOut = {5, Range{0,100}, Step 1,
+    Name "}Dimensions/Magnet/Out-of-rotor thickness [mm]"}
+  lGapRotor = {7, Range{1,100}, Step 1,
+    Name "}Dimensions/Rotor/Gap thickness [mm]"}
+  lGapStator = {3, Range{1,100}, Step 1,
+    Name "}Dimensions/Stator/Gap thickness [mm]"}
+  lAirRing = {1, Range{1,100}, Step 1,
+    Name "}Dimensions/Stator/Air ring thickness [mm]"}
+  lStator = {30, Range{0.1,100}, Step 0.1,
+    Name "}Dimensions/Stator/Thickness [mm]"}
+  lInf = {30, Range{1,100}, Step 1,
+    Name "}Dimensions/Stator/Outside thickness [mm]"}
+  // heights
+  hRotor = {80, Range{1,100}, Step 1,
+    Name "}Dimensions/Rotor/Height [mm]"}
+  hMagnet = {40, Range{1,100}, Step 1,
+    Name "}Dimensions/Magnet/Height [mm]"}
+  hTot = {130, Range{1,100}, Step 1, Closed 1,
+    Name "}Dimensions/Total height [mm]"}
+];
+
+lRotor *= mm;
+lMagnetIn *= mm;
+lMagnetOut *= mm;
+lGapRotor *= mm;
+lGapStator *= mm;
+lAirRing *= mm;
+lStator *= mm;
+lInf *= mm;
+hRotor *= mm;
+hMagnet *= mm;
+hTot *= mm;
 
 // initial rotor bloc
 Cylinder(1) = {0,0,0, 0,0,hRotor, lRotor, AnglePole};