Interestingly enough we must learn the kama at as part of our blue belt. But when we become green belts we're give the option of learning both Bo and Nunchuka. However of the optional classes, the bo is the least well attended. My understanding is that more people find the kata's associated with the bo more difficult. I however love the bo and if I had to make one choice, bo it would be. While I'm not sure I believe we need to master at least 1 of our optional weapons for our BB fylcon