Grodan DM6.5G 100mm (4") Cube With 27/35 Small Hole 4" Cube with Small Hole. Grodan cubes are designed to take SBS or similar propagator cubes, which can then be used on their own or placed on a larger stonewool slab. Three sizes of cubes are available each accommodating a different plug size. The 3" cubes are generally used for tomatoes while the 4" cubes are generally used for peppers and cucumbers and larger root zone or longer term crops.