diff --git a/web/app/3d/ctrl.js b/web/app/3d/ctrl.js
index 793c8333..bc6c3e16 100644
--- a/web/app/3d/ctrl.js
+++ b/web/app/3d/ctrl.js
@@ -181,7 +181,7 @@ TCAD.UI.createCutExtrudeWizard = function (isCut, app, face, alignComponent, ini
   var folder = new tk.Folder(isCut ? "Cut Options" : "Extrude Options");
   tk.add(box, folder);
   var theValue = new tk.Number(isCut ? "Depth" : "Height", def(0, 50));
-  var scale = new tk.Number("Expansion", def(1, 1), 0.1);
+  var scale = new tk.Number("Expansion", def(1, 1), 0.1, 1);
   var deflection = new tk.Number("Deflection", def(2, 0), 1);
   var angle = new tk.Number("Angle", def(3, 0), 5);
   var wizard = new TCAD.wizards.ExtrudeWizard(app.viewer, polygons);
diff --git a/web/app/app-init.js b/web/app/app-init.js
index 67edabb5..bc3fef3d 100644
--- a/web/app/app-init.js
+++ b/web/app/app-init.js
@@ -104,9 +104,12 @@ function start() {
       }
     });
 
-  var dimScale = new TCAD.toolkit.Number("Dim Scale", 1);
+  var dimScale = new TCAD.toolkit.Number("Dim Scale", 1, 0.1, 1);
+  dimScale.min = 0.1;
   app.dock.views['Properties'].node.append(dimScale.root);
-  
+  dimScale.input.on('t-change', function() {
+    app.viewer.dimScale = $(this).val();   
+  });
 }
 window.___log = function(log) {
     $('#log').append( " *****************<br><br><br><br>");
diff --git a/web/app/sketcher/canvas.js b/web/app/sketcher/canvas.js
index 7211d7b3..272a43e8 100644
--- a/web/app/sketcher/canvas.js
+++ b/web/app/sketcher/canvas.js
@@ -106,6 +106,9 @@ TCAD.TWO.Viewer = function(canvas) {
   this._serviceLayers = [];
   this.dimLayer = new TCAD.TWO.Layer("_dim", TCAD.TWO.Styles.DIM);
   this.dimLayers = [this.dimLayer];
+  this.bus.defineObservable(this, 'dimScale', 'dimScale', 1);
+  this.bus.subscribe('dimScale', function(){ viewer.refresh(); });
+  
   this._workspace = [this.dimLayers, this.layers, this._serviceLayers];
   this.toolManager = new TCAD.TWO.ToolManager(this, new TCAD.TWO.PanTool(this));
   this.parametricManager = new TCAD.TWO.ParametricManager(this);
diff --git a/web/app/sketcher/shapes/dim.js b/web/app/sketcher/shapes/dim.js
index 4b049a3b..c2b53143 100644
--- a/web/app/sketcher/shapes/dim.js
+++ b/web/app/sketcher/shapes/dim.js
@@ -23,8 +23,8 @@ TCAD.TWO.LinearDimension.prototype.getB = function() { return this.b };
 
 TCAD.TWO.LinearDimension.prototype.drawImpl = function(ctx, scale, viewer) {
 
-  var off = 30;
-  var textOff = 3;
+  var off = 30 * viewer.dimScale;
+  var textOff = 3 * viewer.dimScale;
 
   var a, b, startA, startB;
   if (this.flip) {
@@ -65,7 +65,7 @@ TCAD.TWO.LinearDimension.prototype.drawImpl = function(ctx, scale, viewer) {
   function drawRef(start, x, y) {
     var vec = new TCAD.Vector(x - start.x, y - start.y);
     vec._normalize();
-    vec._multiply(7);
+    vec._multiply(7 * viewer.dimScale);
     
     ctx.moveTo(start.x, start.y );
     ctx.lineTo(x, y);
@@ -92,7 +92,7 @@ TCAD.TWO.LinearDimension.prototype.drawImpl = function(ctx, scale, viewer) {
 //  drawArrow(_ax, _ay);
 //  drawArrow(_bx, _by);
 
-  ctx.font="12px Arial";
+  ctx.font= (12 * viewer.dimScale) + "px Arial";
   var txt = d.toFixed(2);
   var h = d / 2 - ctx.measureText(txt).width / 2;
 
diff --git a/web/app/ui/toolkit.js b/web/app/ui/toolkit.js
index 81f8a2cf..3303505d 100644
--- a/web/app/ui/toolkit.js
+++ b/web/app/ui/toolkit.js
@@ -71,11 +71,14 @@ TCAD.toolkit.propLayout = function(root, name, valueEl) {
     .append(valueEl));
 };
 
-TCAD.toolkit.Number = function(name, initValue, baseStep) {
+TCAD.toolkit.Number = function(name, initValue, baseStep, round) {
   this.root = $('<div/>', {class: 'tc-row tc-ctrl tc-ctrl-number'});
   this.input = $("<input type='text' value='"+initValue+"' />");
   this.slide = false;
   baseStep = baseStep || 1;
+  round = round || 0;
+  this.min = null;
+  this.max = null;
   var scope = this;
   var lastValue = null;
   function trigger() {
@@ -84,13 +87,13 @@ TCAD.toolkit.Number = function(name, initValue, baseStep) {
       lastValue = $(this).val();
     }
   }
+  
   this.input.on('input', function(e) {
     var val = $(this).val();
-    try {
-      parseFloat(val)
-    } catch (e) {
-      $(this).val(val.replace(/[^0-9\.]/g, ''));
-    }
+    //var floatRegex = /[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?/;
+    //if (!floatRegex.test(val)) {
+    //  $(this).val(val.replace(/[^0-9\.-]/g, ''));
+    //}
     trigger.call(this);
   });
   this.input.get(0).addEventListener('mousewheel', function (e) {
@@ -104,6 +107,15 @@ TCAD.toolkit.Number = function(name, initValue, baseStep) {
     if (!val) val = 0;
     var step = baseStep * (e.shiftKey ? 100 : 1);
     val = parseFloat(val) + (delta < 0 ? -step : step);
+    if (scope.min != null && val < scope.min) {
+      val = scope.min;
+    }
+    if (scope.max != null && val > scope.min) {
+      val = scope.max;
+    }
+    if (round !== 0) {
+      val = val.toFixed(round);
+    }
     $(this).val(val);
     e.preventDefault();
     e.stopPropagation();
@@ -205,3 +217,19 @@ TCAD.Bus.prototype.notify = function(event, data) {
     }
   }
 };
+
+TCAD.Bus.Observable = function(initValue) {
+  this.value = initValue;
+};
+
+TCAD.Bus.prototype.defineObservable = function(scope, name, eventName, initValue) {
+  var observable = new TCAD.Bus.Observable(initValue);
+  var bus = this;
+  return Object.defineProperty(scope, name, {
+    get: function() { return observable.value;},
+    set: function(value) { 
+      observable.value = value;
+      bus.notify(eventName, value);
+    }
+  });
+};
\ No newline at end of file