Mini tigernuts are graded between 6mm and 8mm. For something totally different try soaking and cooking your tigers in coca cola.
CAUTION: All dry particles and nuts will absorb water and expand once submerged, for this reason they MUST all be prepared correctly (Soaked for a given time and cooked for a given time). Failure to prepare properly can be deadly to fish.
TO PREPARE: Soak for a minimum of 24 hours then boil vigorously for 30 minutes. If you leave the prepared Tiger nuts in an air tight bucket/container for a few days after boiling they will start to ferment, the water will turn gloopy/milky due to all the sugars in the nuts being released.
Note: Once cooked you can also add liquid foods, oils or bait additives of your choice to add even more attraction.