diff --git a/js/gravity-force-lab-basics/view/GFLBMassControl.js b/js/gravity-force-lab-basics/view/GFLBMassControl.js
index 572e749..40a4a8c 100644
--- a/js/gravity-force-lab-basics/view/GFLBMassControl.js
+++ b/js/gravity-force-lab-basics/view/GFLBMassControl.js
@@ -38,11 +38,12 @@ define( require => {
      * @param {Range} massRange
      * @param {String} labelContent - a11y, the content of the label for the mass control
      * @param {ISLCObjectEnum} thisObjectEnum
+     * @param {GFLBAlertManager} alertManager
      * @param {GFLBMassDescriber} massDescriber
      * @param {Tandem} tandem
      * @param {Object} [options]
      */
-    constructor( titleString, valueProperty, massRange, labelContent, thisObjectEnum,
+    constructor( titleString, valueProperty, massRange, labelContent, thisObjectEnum, alertManager,
                  massDescriber, tandem, options ) {
 
       options = merge( {
@@ -55,6 +56,9 @@ define( require => {
         tandem: tandem.createTandem( 'titleText' )
       } );
 
+      // Keep track of the current mass between the start and end of an interaction to see if we should alert.
+      let currentMass = valueProperty.value;
+
       const numberPicker = new NumberPicker( valueProperty, new Property( massRange ), {
         font: new PhetFont( 20 ),
         scale: 1.5,
@@ -72,7 +76,20 @@ define( require => {
         // a11y
         pageKeyboardStep: BILLION_MULTIPLIER * 2,
         accessibleName: labelContent,
-        a11yCreateAriaValueText: () => massDescriber.getMassAndUnit( thisObjectEnum )
+        a11yCreateAriaValueText: () => massDescriber.getMassAndUnit( thisObjectEnum ),
+
+        // on end interaction, if alert a special alert if the mass started at the min/max and didnt' change.
+        a11yCreateValueChangeAlert: () => {
+
+          // no change and at max or min
+          if ( currentMass === valueProperty.value && ( currentMass === massRange.max || currentMass === massRange.min ) ) {
+            return alertManager.alertMassMinMaxEdge( thisObjectEnum );
+          }
+          return null; // regular mass changed alerts come from model changes
+        },
+        startChange: () => {
+          currentMass = valueProperty.value;
+        }
       } );
       const numberPickerLabel = new Text( billionKgString, {
         font: new PhetFont( { size: 14 } ),
diff --git a/js/gravity-force-lab-basics/view/GFLBScreenView.js b/js/gravity-force-lab-basics/view/GFLBScreenView.js
index 8873bb3..6a42f7b 100644
--- a/js/gravity-force-lab-basics/view/GFLBScreenView.js
+++ b/js/gravity-force-lab-basics/view/GFLBScreenView.js
@@ -95,7 +95,7 @@ define( require => {
       // initialize a11y describers and alert manager
       const positionDescriber = new GFLBPositionDescriber( model, mass1LabelString, mass2LabelString );
       const forceDescriber = new GFLBForceDescriber( model, mass1LabelString, mass2LabelString, positionDescriber );
-      const massDescriber = new GFLBMassDescriber( model );
+      const massDescriber = new GFLBMassDescriber( model, forceDescriber );
       const alertManager = new GFLBAlertManager( model, massDescriber, forceDescriber );
 
       super( {
@@ -172,10 +172,10 @@ define( require => {
 
       // mass controls
       const massControl1 = new GFLBMassControl( mass1String, model.object1.valueProperty,
-        GFLBConstants.MASS_RANGE, mass1ControlLabelString, OBJECT_ONE,
+        GFLBConstants.MASS_RANGE, mass1ControlLabelString, OBJECT_ONE, alertManager,
         massDescriber, tandem.createTandem( 'massControl1' ) );
       const massControl2 = new GFLBMassControl( mass2String, model.object2.valueProperty,
-        GFLBConstants.MASS_RANGE, mass2ControlLabelString, OBJECT_TWO,
+        GFLBConstants.MASS_RANGE, mass2ControlLabelString, OBJECT_TWO, alertManager,
         massDescriber, tandem.createTandem( 'massControl2' ), {
           color: new Color( 255, 0, 0 )
         } );
diff --git a/js/gravity-force-lab-basics/view/describers/GFLBMassDescriber.js b/js/gravity-force-lab-basics/view/describers/GFLBMassDescriber.js
index 7400220..1cfa2f3 100644
--- a/js/gravity-force-lab-basics/view/describers/GFLBMassDescriber.js
+++ b/js/gravity-force-lab-basics/view/describers/GFLBMassDescriber.js
@@ -24,8 +24,9 @@ define( require => {
 
     /**
      * @param {GFLBModel} model
+     * @param {ForceDescriber} forceDescriber
      */
-    constructor( model ) {
+    constructor( model, forceDescriber ) {
 
       const options = {
         object1Label: mass1LabelString,
@@ -34,7 +35,7 @@ define( require => {
         formatMassValue: mass => StringUtils.fillIn( massBillionsPatternString, { mass: mass } )
       };
 
-      super( model, options );
+      super( model, forceDescriber, options );
     }
   }