Mitoku Traditional Natto Spores
Product Review (submitted on April 2, 2014):
I've been very happy with the several batches of natto I've made with this product. The only downside is that it's pure spore, which means you have to mix a very tiny amount of product very throughly into a very large amount of beans. (0.1 grams spore to 1 kilo beans (before cooking)).
Luckily, a hilariously small spoon is included with the spore for measuring. My kitchen scale doesn't get down to 0.1 grams.
I will definitely be buying this again.