Explain out-of-stock options
Tell shoppers whether the option they pick can still be ordered.
Each example below is the actual published output of the Variation backorder policy widget for a sample product, a Sable brush set: Small is out of stock but can be backordered, Medium is in stock and Large is out of stock without backorders. On a product page the message follows the size the shopper picks.
The Small set (out of stock, backorders allowed): Can be ordered now and sent when back in stock.