What is the recommended stirring bar for GreenHouse?

For the current GreenHouse Plus, we recommend:

• RR99613: Pivot Ring Stirring Bar 15 mm (Pack of 40)

For the older GreenHouse Classic, with slightly narrower tubes, the following is advised instead:

• RR99607: Pivot Ring Stirring Bar 12 x 4.5 mm (Pack of 40)