What is it? 
Seasoned rice vinegar.

What is it used for?
Making sushi rice, also used in dressings.

Is it easy to find?
Sushi is becoming more and more popular all over the world. Lots of supermarkets stock sushi seasoning. If you can’t find it rice vinegar is very widely available and can be seasoned to make sushi vinegar (see below).

Can it be substituted?
You can add a little salt and sugar to normal rice vinegar.