Honda FourTrax Foreman Rubicon TRX520FM6 2020 Owner's Manual page 182

Brakes
RIGHT REAR
(4)
(3)
(3) wear indicator (4) reference mark
Check the wear indicator. If the wear indicator (3) aligns with the
reference mark (4), replace both pads as a set, see your dealer for
this service.
172 Servicing Your Honda