Yeah that one ;) But gladly I just realized that litres are not an SI unit either.

WHAT? Of course they are, they just aren't a base unit.

Wikipedia says they're not an official SI unit. However they work quite well with the SI units.

Wow that's a weird exception; https://en.wikipedia.org/wiki/Litre

I was always tought that the liter was an SI unit, I mean, it's defined in terms of SI units, I know it's not a base unit, but weird that it's singled out as "well, you're technically SI compatible, and you're defined in SI units, but we're not gonna let you be part of the group" :)

It even has an official SI symbol (L), despite not being an SI unit, what?!

Unrelated: "The kilogram is the mass of a litre of cold water; a cubic centimetre or millilitre of water has a mass of one gram"

So satisfying...

Call them dm^3 (or cm^3 for ml).