The Inventory Stock Control allows you to monitor inventory counts and notify customers:

Stock Control Modes When your inventory stock gets low or runs out, the shopping cart has several different options to edit what the customer sees.  This is a good to notify customers of inventory availability.   None Has no stock control monitoring at all. The shopping cart will still keep track of the amount of stock for each item, but the customer will not see a difference regardless of the amount of inventory in stock. Transparent The customers won't know anything about stock, but the administrator of the shop will still be emailed when stock is low. Visible This option shows customer when they are ordering more than is in stock and display a custom message, This option does ALLOW them to order, and the administrator also receives an email. Restricted This option shows customer when they are ordering more than is in stock , and then the shopping cart gives a custom message. It DOES NOT PERMIT THEM TO BUY the out-of-stock product. The administrator does receive an email. Restricted Hidden This option does not show out of stock items to customers, and the administrator does receive an email.

Out of Stock Message This message is the custom message that customers will see depending on the inventory control option selected. Set Limit (in Units) This is the limit for the shopping administrator to receive an email. Show Inventory Counts to Shoppers This allows you to show customers the inventory count. One nice feature is to show the customer only when it is below a certain amount. Some shop administrators use this to create a sense of urgency on the part of the customer. Other shop administrators prefer to keep their inventory counts hidden.