This performance Dr. Pulley HiT clutch is specifically made for the GY6 150cc engine.  The DR. PULLEY clutch does NOT come with the outer clutch drum. 

Clutch Outer diameter: 122mm - for use with 125mm ID clutch bell. 
Center opening: Width - 28mm; Height - 24mm

The Dr Pulley HiT clutch has high-quality Kevlar clutch pad material running the length of the clutch arms for maximum surface area engagement with the clutch bell.

Additionally, the HiT clutch has a secondary mechanism that engages when your CVT system reaches a certain RPM (tunable with the included three sets of "pillow" springs). This secondary mechanism locks the clutch arms in place against the clutch bell preventing clutch slippage when under load! 

The result? Solid clutch engagement at all times, particularly when accelerating and climbing. This clutch is designed to be tuned to your vehicle and comes with a total of six sets of springs - three clutch arm spring sets, and three pillow spring sets.

Hammerhead part # c181401
Dr. Pulley HiT Performance Clutch Gy6 150-232cc p/n 181401