Cavi, 4ls means Four Leading Shoe, leading as opposed to trailing,
In old car drum brakes, one shoe leads, the other follows, since each is actuated from the same end. Multi Leading shoe designs means there is an actuator in more than one place, pressing the shoes out against the drum so that the rotation of the drum is going AT the raised edge of the shoe.
Stick a broomstick in your fist & twist it, proof direction matters, tho it will tend to make ya think opposite of whats happenin inside a drum brake.