This SDK is a Ruby wrapper to integrate ShipStation with Spree. It enables ShipStation to pull shipments from the system and update tracking numbers. ShipStation is a shipping service that provides order fulfillment for online retailers. It integrates with USPS, UPS, and FedEx for retrieving rates, creating shipping labels, and more. ShipStation provides a way to ship using branded tracking page shipping software for wherever you sell, however you ship.