WooCommerce Quantity Dropdown Plugin allows you to add a dropdown on product and shop pages for product quantity. You can enable product quantity dropdown on specific categories and products as well. WooCommerce quantity dropdown plugin lets you adjust the minimum and maximum quantity order to sell products. You can set the step to offer quantity for each product like, if you set 2 then product quantity will be displayed as 2, 4, 6, 8, etc.  The price of this extension is just $19 with a money-back guarantee.