The AO36/40 1.5" rockwool propagation cube comes in a sheet of 98 cubes, which fits nicely into a standard 10" x 20" greenhouse flat. They are most commonly used for starting tomatoes, cucumbers, and other long-term crops.
These cubes are designed to fit into the DM4-G, DM6-G, and DM10-G blocks.
Cubes are roughly 1.5 in. x 1.5 in. x 1.5 in.