The open class features courses with different levels of difficulty and length. You can pick the one that you prefer, and find most suitable. You can also register on site and start whenever you want. 

Age- and gender-divided classes, on the other hand, have a specific level of difficulty and length based on the competitive distance. The age range is 10 to 95. Compared to the open class, you need to register in advance, and will be assigned a specific start time.