How to distinguish the size of stringing pulley

Usually, we struggle to choose the size of the stringing pulley when we choose it. Today,  Marshine team teaches customer how to distinguish the size of the stringing pulley. Generally, the size of the pulley is determined by the diameter. Generally, there are several diameters, namely 508mm, 660mm, 822mm, etc. as long as we look at the diameter parameters, we can buy a paying off pulley suitable for our own project