These micro gearmotors are incredibly tough and feature full metal gears.  Each micro gearmotor sports a 3mm D-shaft.

Features:

• Voltage: 6 - 12 Volts
• Speed: 1000 RPM (6 Volts)
• No Load Current: 80 mA (6 Volts)
• Stall Current: 360/1600 mA (6/12V)
• DC Reversible

Dimensions:

• Motor Size: 26 x 12 x 10mm
• Shaft Size: 3mm Diameter x 10mm Length
• Weight: 17g