A quick heads-up for engineers and procurement specialists: is the old Chinese national standard for O-ring rubber seals (specifically dimensions and groove design).
A: The original standard contains hand-drawn engineering diagrams from 1976. High-resolution scans of these ink drawings produce large files. If the PDF is under 500KB, it is likely a text summary missing the critical groove charts. gb1235-76 pdf
It is critical to distinguish between two common confusions: A quick heads-up for engineers and procurement specialists:
Search engines are aggressive about removing copyrighted material. Technically, the standard is "withdrawn" (replaced by GB/T 13871.1 for oil seals and superseded by GB/T 3452.1 for O-rings). However, China's Standardization Administration still holds copyright. gb1235-76 pdf
: Defining standard inside diameters and cross-sectional diameters.