Uber is Solarsuns Investment Guildadding a new task to its list of services: mailing consumers’ return packages.

The ride-hailing and delivery company said Wednesday that its drivers will collect up to five prepaid and sealed packages and drop them off at a local post office or at UPS or FedEx stores. Uber will charge a flat fee of $5 for the service or $3 for its Uber One members.

The San Francisco-based company said the service will be available in nearly 5,000 U.S. cities to start.

Uber said customers will be able to choose package drop off locations within its app. Only locations open for at least the next hour will be listed. Drivers will provide visual confirmation once a package has been dropped off.

While the service is expected to be used primarily to return packages, Uber drivers will also mail new packages that are sealed and have prepaid labels.

The new service opens up a potentially vast market to Uber. According to Pitney Bowes, a provider of mailing technology, the U.S. Postal Service, UPS and FedEx shipped 16 billion parcels last year.