# Step 5: Add a template constraint to limit instance size
<a name="getstarted-constraint"></a>

Constraints add another layer of control over products at the portfolio level. Constraints can control the launch context of a product (launch constraints), or add rules to the CloudFormation template (template constraints). For more information, see [Using AWS Service Catalog Constraints](constraints.md).

Add a template constraint to the Linux Desktop product that prevents users from selecting large instance types at launch time. The development-environment template allows the user to select from six instance types; this constraint limits valid instance types to the two smallest types, `t2.micro` and `t2.small`. For more information, see [T2 Instances](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/t2-instances.html) in the *Amazon EC2 User Guide*.

**To add a template constraint to the Linux Desktop product**

1. On the **Portfolio details** page, choose **Constraints**, then choose **Create constraint**.

1. In the **Create constraint** page, for **Product,** choose **Linux Desktop**. Then, for **Constraint type**, choose **Template**.

1. In the T**emplate constraint** section, choose **Text editor**.

1. Paste the following into the text editor:

   ```
   {
     "Rules": {
       "Rule1": {
         "Assertions": [
           {
             "Assert" : {"Fn::Contains": [["t2.micro", "t2.small"], {"Ref": "InstanceType"}]},
             "AssertDescription": "Instance type should be t2.micro or t2.small"
           }
         ]
       }
     }
   }
   ```

1. For **Constraint description**, enter **Small instance sizes**.

1.  Choose **Create**.