If none of the available ticket template sizes that are offered when creating ticket templates suits your needs, you can install this add-on and define your own.
Once you install this add-on, head to the Tickera > Settings > Miscellaneous and set the value for "Add additional ticket template size" field.
Let's say that you want to create a template which has a width of 150mm and height of 215mm. You should set the value of that field to 150x215 in that case and that's it!
Now you should see your custom ticket template size when you edit ticket template.
Add-on is installed and activated like any other WordPress plugin and works with Tickera as a "standalone" as well as when used accompanied by WooCommerce via Bridge for WooCommerce.