# Building Your Mobile Integration

Learn about Finix's mobile in-person payments integrations.

PAX D135 Bluetooth card reader with Finix branding
The Pax D135 is a compact, mobile smart card reader designed for modern businesses on the go. Whether you're accepting payments in-store or out in the field, the D135 connects seamlessly to your Android or iOS device via Bluetooth, transforming your phone or tablet into a powerful payment terminal.

For additional details on the Pax D135, see [Pax D135 Overview](/guides/in-person-payments/select-your-device/pax-d135).

Finix offers integration choices for mobile payments:

1. Android SDK for Pax D135
2. iOS SDK for Pax D135


## Important Pre-Requisites

Device Designation
A D135 device can be designated to be used for either Sandbox development or Production transaction processing but not both. We recommend requesting enough devices to utilize in both your Sandbox development and Production testing.

When ordering a Pax D135 your Finix point of contact will have you designate which environment you wish to use it in. Finix will notify you which device serial number corresponds to each environment.

## Device Limits

The D135 card reader allows accepting payments via Tap, Insert, or Swipe. Tap can be accepted as long as the amount is less than $1000. For larger amounts card should be inserted into the card reader.

## Learn More

Android SDK
iOS SDK