The G2G Rockwool 6”x6“x4” Block is used as a shorter alternative to the G2G Rockwool 6“ Cube. Typically used in industrial hydroponic setups, the G2G 1.5“ Propagation Plugs fit perfectly into the 1.5” diameter hole included in the 6“x6”x4” block. Every block has uniform firmness, density, and fibrous structure which ensures an even distribution of nutrients, water and pH levels.