NEMA 11 closed loop motor rear shaft 28HS51-2004B-E1000 has a frame size 28-51mm , equipped with a 1000cpr incremental optical encoder & a length of 12.5mm rear shaft, has a rated current of 1.0A and a holding torque of 0.12Nm. It offers higher accuracy, higher output torque, higher speed, lower motor heating, lower power consumption, and faster response to drive controllers compared to open loop stepper motors. Recommended Drive: Leadshine CL42C Closed-Loop Stepper Motor Drive

NEMA 11 closed loop motor rear shaft Specification

• Part Number: 28HS51-2004B-E100
  Step Angle: 1.8deg
  Bipolar/Unipolar: Bipolar
  Holding Torque: 0.12Nm
  Rated Current/phase: 2.0A
  Driving Voltage: 12-24VDC
  Frame Size: 28x28mm
  Body Length: 69.5mm
  Front Shaft Diameter: Φ5mm
  Front Shaft Length: 20mm
• Rear Shaft Diameter: Φ5mm
  Rear Shaft Length: 12.5mm
• Encoder Type: Incremental Optical
  Encoder Resolution: 1000CPR

Overall Size

If need motor + encoder + gearbox, we recommend the model 28AI32EC-HGXX as below link.
NEMA 11 Closed-loop Stepper Motor with Gearbox 32mm 1A (frankhuai.com)