kind of each gear is free to spin on mainshaft ,snchro hubs are splined to shaft ,each gear has a ring of dog teeth these are coffin shaped ,each synchro hub has a sleeve with coffin shaped teeth which slide over gear dog teeth to lock gear to mainshaft giving you that gear ,to match the speed of hub and gear ,gear has cone in front of dog teeth and betwween hub and gear is baulk ring which is aldo cone shaped and has triangled shape teeth ,hub pushes baulk ring against gear cone aligning speeds and the triangle teeth aline synchro hub sleeve to gear dog teeth,dog teeth are coffin shaped so that they teeth can mesh going into gear and so tha=t when your in gear the greater the power the more there pulled into gear ,this can be seen when holding gear stick and accelerating you can feel gear stick been pulled further into gear ,apart from late series 3s there gear teeth were straight a dont have this effect and can jump out of gear if accelerating too hard or slowing down too quick