Grodan Rockwool SBS TrayOverview The Grodan SBS Tray is ideal for seed germination or propagating cuttings. The single block system is supplied in a plastic tray for easy handling. General Information Once young plants are rooted, they can then be transferred to a larger cube or your preferred growing medium. Available in two sizes, 1" and 1. 5". Both are compatible with all Grodan Delta Cubes. A full box of the 1" SBS contains 2700 cubes. The 1. 5" box contains 1386 cubes.