Shein has emerged as a major threat to established fast fashion retailers like Zara and H&M. In 2022, Shein generated about $23 billion in global revenue, accounting for nearly one-fifth of the global fast fashion market and outpacing Zara and H&M. Shein's competitive advantages include its ultra-flexible supply chain that allows for small initial orders that can quickly scale based on demand. This is different from Zara and H&M's model of pre-ordering large volumes 3-12 months in advance. Shein introduced 1.5 million new products to the US market from Nov 2022-Nov 2023, compared to 40,000 for Zara and 23,000 for H&M. Shein's product variety is seen as a major advantage.