The 1.5” size fits perfectly in the Gro-Smart tray as well as all our pre-drilled Gro-Blocks.One advantage of using the Gro-Smart tray is that it elevates the plugs above the waterline and ensures good airflow around the plugs.A-Ok plugs come labeled with instructions in a shrink-wrapped package that fits a standard 10 x 20 tray (flat). Total of 98 plugs by sheet.