These light-weight brackets are specifically designed for the Pololu 37D mm metal gearmotors, such as the 19:1 metal gearmotor 37Dx52L mm. Each bracket features fourteen mounting holes (seven along each edge) for M3 or #4-size screws, giving you a variety of mounting options. A total of twelve M3 screws (six for each bracket) are included for securing the motors to the brackets (motor mounting pitch diameter 31mm).