Premium Plum Sauce (often available in 500 g quantities) is a sweet and tangy condiment widely used in Cantonese and wider Chinese cuisine. It is typically made from a base of preserved plums, sugar, vinegar, salt, ginger, and chili peppers, resulting in a thick, jam-like consistency. 

Key Characteristics
Flavor Profile: A balanced sweet-tart taste with mild savory and spicy notes.
Texture: Viscous and smooth, similar to a rich jam or fruit puree.
Common Ingredients: Salted plums, sugar, water, rice vinegar, ginger, and chili. 

Common Uses
The sauce is highly versatile and serves several purposes in Asian cooking: 
Dipping: Traditionally served with roast duck (hence why it is sometimes called “Duck Sauce”), spring rolls, egg rolls, dumplings, and fried wontons.
Glazing & Marinating: Used as a glossy glaze for grilled meats like pork ribs and poultry, or as a marinade to tenderize and add flavor.
Stir-Frying: Added to noodle or vegetable dishes for an instant flavor boost. 

Popular Brands and Options
While various manufacturers produce this sauce, several are prominent in the 500 g or similar size category: 
Lee Kum Kee: While their most common retail size is 260 g, they also offer larger bulk formats (e.g., 2.31 kg) and are frequently paired with their 500 ml premium soy sauces.
Woh Hup: Often sold in 400 g jars, their version is noted for being fat-free and Halal-certified.