Concrete blocks, hollow [CBH] - jcgomezz/Building_taxonomy GitHub Wiki

Concrete blocks with two or more cells (cavities) comprising more than 30% of the volume, which may be grouted and reinforced.

Hollow concrete blocks, Peru (S. Brzev)

Hollow concrete blocks with three cells, Haïti (front) and with two cells, Canada (rear), (S. Brzev)