20.4:1 Metal Gearmotor (25D×50L) HP 12V, 500 RPM

Need a compact 12V DC gearmotor that’s fast enough for small robots, but still has real torque? The Pololu 3203 pairs a high-power 12V brushed DC motor with a 20.4:1 metal spur gearbox, giving you a punchy balance of speed and strength in a ~25mm diameter body. 

Why you’ll like it

• Great speed/torque balance for small mobile robots (fast, but not “weak”). 
• All-metal spur gearbox for durability in hobby robotics. 
• Standard 25D form factor makes swapping ratios easier across the 25D family. 
• Upgradeable option: also available with integrated encoder (handy for speed/position feedback).

Technical specifications

Pinout & power notes

• This is a brushed DC motor: connect to a suitable DC motor driver (H-bridge) to control direction and speed (PWM).
• Avoid stalls/overload: Pololu notes stall values are theoretical; recommended upper limit is 4 kg·cm continuous and 8 kg·cm intermittent. :contentReference[oaicite:20]{index=20}
• Rule of thumb: for brushed motors, keep operating current around ≤25% of stall current to reduce overheating risk.

FAQ

• Can I run it below 12V?

  Yes—brushed DC motors generally run above/below nominal voltage, but performance changes and higher voltages can reduce motor life. 

• What driver should I use?

  For the HP 25D versions, Pololu recommends VNH5019-based motor drivers 

• What wheels fit the shaft?

  It’s a 4mm output shaft—use 4mm hubs/adapters (e.g., aluminum hub, multi-hub wheels, scooter/hex adapters). 

• Important mounting warning?

  Don’t screw more than 6mm into the mounting holes—screws can hit the gears.