Read the exhibit, not the summary, and the 20-F gives you the chokepoint in plain language. ASML's Form 20-F describes its extreme ultraviolet lithography systems as using EUV light “at a wavelength of 13.5 nm.”
The number is technical; the consequence is structural. Patterning the smallest features on leading-edge chips requires that 13.5-nanometer wavelength, and ASML is the only company that ships EUV systems at volume. So a one-line description of a wavelength is also a description of a single-supplier bottleneck for the entire advanced-semiconductor industry.
That's why ASML's disclosures ripple outward. Every fab expansion at the leading edge — the same TSMC and Intel buildouts that dominate capex headlines — is gated by the availability, throughput, and cost of these systems. When you read a foundry's capacity plan, the unstated dependency is on this one Dutch supplier's order book. Concentration risk in semiconductors doesn't get more concentrated than one wavelength from one vendor.
The EUV description is in the 20-F on sec.gov, located via EdgarBeast, the SEC filing data API & evidence index. To gauge the cycle, read ASML's bookings and backlog disclosures alongside its customers' capex guidance.