This one set of gears can produce all of those totally different gear ratios without having to engage or disengage another gears. With two of those gearsets in a row, we are in a position to get as many ahead gears and one reverse gear as our transmission needs browse around here. This profile has the essential property of maintaining a constant velocity ratio between the 2 gears. Like the peg wheel above, the contact point strikes, however the shape of the involute gear tooth compensates for this motion.