Product Specs: #41 Chain, 10T Noram 1600 Series Clutch 3/4" bore, 3/16" keyway Standard Sprocket Engagement at 2100 rpm Bore is 2.5" Deep Overall OD is 4.7" Rated for 3-15 HP Engines Stock Engagement: 2050 Stock Spring: Purple Can be mounted Inboard or Outboard Made by Noram **There are many variables that play into the performance of a clutch. Tire size, rear sprocket size and rear drive set-up are a few of the main variables that could affect clutch performance. If you are using large tires or a small sprocket, your vehicle may require a belt drive system. Clutch performance is not based soley on the engine size.**