This is the MotoTec Universal Parts QMB139 PERFORMANCE CLUTCH, 151-275.

Universal Parts Performance Clutch for 50cc QMB139 4-stroke engines. Comes with 2000 RPM springs installed.

Product Specifications:

• SKU: 151-275
  
• Inner Diameter (Flat Side to Flat Side): 24mm
  
• Inner Diameter (Round Side to Round Side): 28mm
  
• Overall Outer Diameter: 105mm
  
• 2000 RPM Clutch Springs