soba made with 20% wheat flour and 80% buckwheat flour
A traditional ratio for soba noodles; the name comes from 'two' (wheat) and 'eight' (buckwheat).
See also: そば
The nihachi soba at this shop has a nice aroma.
十割蕎麦 is made with 100% buckwheat flour, while 二八蕎麦 contains 20% wheat flour, making it easier to handle and giving a different texture.
The name 二八 (two-eight) refers to the traditional ratio of two parts wheat flour to eight parts buckwheat flour.