[[P3045R8]](https://wg21.link/p3045r8) supplies the type system. It does not supply the SI. A user who includes the framework gets `quantity` , `unit` , `quantity_spec` , `prefix` — but no `metre` , no `kilogram` , no `second` . The framework is deliberately content-agnostic: it supports arbitrary systems of quantities and units. Shipping the framework without SI content would be like shipping `<algorithm>` without `<vector>` — or the coroutine framework without `std::task` .