The general rule of thumb is that the 20L pots are good for 50-60cm centres, while the 36L pots are good for 60-75cm. The same method can be applied to RAIN/AERO 15L & 30L and EasyFeed 16, 22, 30L pots. All of our systems have the option to locate the header pot outside of the grow space, maximising yield potential.