The Out of Stock Module in OpenCart allows more efficient management of out-of-stock products for store owners by offering, for instance, back-in-stock notifications, stock alert functionality, and alternative product suggestions to the buyer. This module has an ability to be designed to send customised messages based on availability and automatically update the inventory status by predefined rules.

The module typically offers:

1. Back-in-Stock Notifications: This feature lets customers subscribe to alerts on out-of-stock products. When the item is back in stock, the module automatically notifies interested customers, making the chances of conversion for those potential sales much higher.
2. Stock Alerts for Admin: The module alerts the admin when stock levels come low or are exhausted, thus enabling timely restocking and averting long periods of stockouts.
3. Alternative Product Suggestions: If a product is sold out, it can automatically suggest similar or alternative products to the consumer to buy, thus ensuring improved shopping experience and potential loss avoidance.
4. Display Custom Messages: The system allows customising messages that can be displayed on a product page, such as when a product will come back in stock, possible alternatives, or back orders. 
5. Automatic Stock Status Updates: With the use of rules, the module automatically updates the stock status either as "Out of Stock" or "Available Soon," which informs the customers without having to update it manually.

Features

1. Automated Notifications for Customers: Email notifications are sent immediately to the customers when products of interest to them are in stock.
2. Admin Alerts: Alerts for low stock are sent to admins, enabling them to take proactive steps on the inventory.
3. Customisable Notifications and Messages: This option provides for customisable messaging. That way, store owners can set up the language and tone of messages for the notification as well as for the storefront. 
4. Alternative Product Recommendations: On the product page, the plugin offers alternative recommendations so that lost sales do not happen, and customers do not get disappointed.
5. Seamless Integration with OpenCart Inventory System: It seamlessly integrates with the OpenCart Inventory System. So updates and notifications occur in real time. 
6. Back-order Options: For products with expected restocks, the module can enable backordering, which means that customers can buy items that are temporarily out of stock. 

Benefits

1. Improves Customer Experience: The module keeps customers informed and provides options, such as alternative suggestions or notifications, thereby improving the experience.
2. Increases Conversion Rates: Using back-in-stock notifications, the customers who would have left the site are encouraged to return and recover potential lost sales.
3. Reduces Inventory Management Hassles: Automated alerts and stock updates reduce the manual work involved in inventory management and prevent prolonged out-of-stock situations.
4. Increases Repeat Visits: Customers are more likely to revisit the store when they know they’ll be notified about desired items or find alternative products they may be interested in.
5. Improves Brand Trust: The module shows customers that the store is responsive to their needs and is committed to keeping them informed and satisfied, fostering trust and loyalty.