NARAKU performance quality piston set. Suitable for all GY6 50cc cylinders [39mm bore]. The NARAKU piston has a molybdenum coating to reduce wear and shorten the running-in period. This piston has been included in all 50cc NARAKU cylinder sets since 2009, and can be easily used as a replacement in Chinese original cylinders. The CNC-machined grooves in the piston skirt ensure continual lubrication. The lubrication hole with sunken oil groove in the small end bearing is technology taken straight from the race track. Advanced piston technology for 4-stroke engines. Piston kit comes complete with rings, oil scraper rings, gudgeon pin and circlips.