If you are comparing Sihoo M59AS vs M18, you are likely trying to find a budget office chair that still feels good after long desk hours. I tested both chairs in my home office in the USA. I used them for work calls, writing, web browsing, and late-night editing. Both chairs offer mesh backs and ergonomic support, but they feel very different in daily use. One feels softer and more relaxed. The other feels more upright and compact. After spending real time with both, I notice