Using YITH WooCommerce Badge Management you can create custom badges you can apply to products in your shop. There are three types of badges: text, CSS, or images.
The integration with YITH Easy Order Page for WooCommerce allows showing your badges also on the grid view and the modal window of the product detail page.
After installing and activating both plugins, you can start creating your badges as described here and assigning them to your products.
