shimano disc rotors, for cargo bikes they come in two sizes, 180mm, cargo 203mm, this will be written on the rotor itself. replace pads when fitting new rotors, keep them very clean. bed the brakes in when you have fitted them before you go down any big hills, (google that for info).

replace when the thickness of the rotor is 1.5mm or less.

SLX 6 bolt model SMRT66M