Yak 52, 50, 18-T Brake Pads
Each main wheel on the three types listed has 12 pucks, retained by small leaf springs.
The thick wedge on the pad's outer wear surface can be inspected by removing the brake drum. This wedge is designed to indicate remaining pad life - or lack of it. By the time your pads are razor thin as shown by the green arrows, you are probably white-knuckling that brake lever, and not getting much braking in return.
It's entirely probable that these Original Russian parts contain asbestos so good maintenance practices for working with brake dust should be observed both during removal and assembly.
Price shown is per brake pad