# Purchase

You can use the Purchase plugin to integrate *in-app purchases* in your App, in combination with the Metrological Billing Server. This way, you can let customers perform transactions in Apps, and the customers can pay for the transactions via the operator’s monthly bill.

> Starting <i>v5.0.0</i> and up, the Purchase plugin is part of the <b>metrological-sdk</b>.<br /><br />For backwards compatibility reasons, the Lightning-SDK exports this plugin provided by the metrological-sdk. The code however is maintained <a href="https://github.com/Metrological/metrological-sdk" target="_blank">here</a>. More information on how to use this plugin can be found <a href="https://github.com/Metrological/metrological-sdk/blob/master/docs/plugins/pin.md" target="_blank">here</a>.