Aftermarket stocks are stocks that are traded during the aftermarket trading hours that occur after the stock market's regular trading hours. The hours when aftermarket stock trading takes place are between 4 p.m. and 6:30 p.m. Eastern.
Aftermarket stocks tend to fluctuate more in terms of price, as the volume of trade is much lower than regular trading hours. A small trade volume can cause a significant gap between bidding and asking prices for stocks, reducing the chances of a favorable price. There is also generally less capital available in the aftermarket stock trading hours, making it difficult to change existing stock into cash.