That’s easier than anything I’ve just told you about. Your chair is asynchronous when you can adjust the backrest and seat independently. For example, if you can tilt your backrest back AND you can tilt your seat and lock it at any angle you like… That’s a chair with an asynchronous mechanism! (Of course, your chair can be asynchronous and still have an off-center tilt mechanism). The advantage of the asynchronous mechanism, however, is that it gives you real freedom in the choice of seat angle. For example, sometimes I tilt my seat back a little, I also tilt the backrest (but not too much) then I add a footrest and play like that (half tilted backwards). I find it extremely pleasant, and since I tend to move around a lot in my chair, I don’t have to move around too much all the time, since gravity keeps me stuck back. This mechanism is available on most high-end gaming chairs.