RS-550s Brushed DC Motor with 3.17mm diameter D-Shaft (9mm Long Shaft) Weight: ~7.7oz (218g) Body Length: 2.24in (57mm) Body Diameter: 1.46in (37.5mm) Operating Voltage: ~6v - 24v Optimal Volt Range: 12v - 18v 18 Volt Nominal (Optimal Power, Speed, and Torque near 18 volts) Shaft Length ~0.35 inch / ~11/32in or ~9mm Diameter ~0.125 inch / 1/8in or ~3.175mm Style: Round Stall Current: ~85A Efficiency: ~70% No Load RPM: ~20000 rpms RPM Peak Efficiency: ~17000 rpms Designed as a Power Tool Drill motor and may replace motors in many 3/8in drills and other cordless and outdoor tools. Popular choice for DIY Electronics and Robotics, PowerWheels, and some Gate Openers. Will not work or fit in all models, be sure to check your specific application's requirements before purchasing PLEASE NOTE: If you're replacing a motor please be sure to verify the motor matches your dimensions and shaft length, style, and diameter before purchasing. Please contact the ProTechTrader directly with questions bef