Billet aluminum drive coupler set for Yamaha Waverunner PWC with the 1.8L 4-stroke engine. These couplers are CNC machined from 6061 aluminum for increased strength over the stock cast aluminum couplers. We finish them with a clear anodizing for years of protection against corrosion. Made for use with the stock rubber damper(not included). One coupler has 30-1.5mm threads and the other has 30-2.0mm threads.