Clue: 1000 + 1 + 50 + 0 + 50? It's about a unit (9)
Answer: KILOLITRE
Explanation: Definition: unit
**K**ilo="1000″; **I**="1″; **L**="50″ in roman numerals; **O**="0″; **L**="50″ again; plus **IT**; plus **RE**="about"