Use the 78-cell side to perfectly fit 1.5" A-OK Starter^TM plugs or round Macroplugs^TM. Use the mesh side for sheets of A-OK's, Mini-Blocks, or Gro-Blocks. The tray fits in a standard 10" x 20" flat and keeps the Grodan elevated from the bottom of the flat. Easily sanitize as any hard-plastic product; it's even dishwasher safe!