Rooting strawberry runners in Jiffy Growblocks is a breeze. We find that the plants don't experience any shock when transplanted. And, they can be placed on top of grow media and will root into the media readily. The ones pictured are 8 cm square. Four fit into a 1010 tray easily. We like the shallow trays. When it rains that growblock doesn't get submerged in water and the tray acts as a reservoir when watered.