I like to buy arrowroot at the bulk food store. It costs a lot to buy it by the bag but lasts a long time. I store it in a rubbermaid bin. I wouldn't take it from the 'bins' because it could be contaminated.

As far as I know, arrowroot only comes in one form. I am happy to be re-educated on that front though.

It's 3/4 cup. I'll go back and edit it. Sorry about that.