Manufactured by Kit Includes 2 Compression Rings 1 Expansion Ring (you get exactly what is pictured) Rings are interchangeable with OEM pistons unless noted Rings are for standard bore size – 40.00mm Compatible with Yamaha models below: 1981 PW50 1982 PW50 1983 PW50 1984 PW50 1985 PW50 1986 PW50 1987 PW50 1988 PW50 1989 PW50 1990 PW50 1991 PW50 1992 PW50 1993 PW50 1994 PW50 1995 PW50 1996 PW50 1997 PW50 1998 PW50 1999 PW50 2000 PW50 2001 PW50 2002 PW50 2003 PW50 2004 PW50 2005 PW50 2006 PW50 2007 PW50 2008 PW50 2009 PW50 2012 PW50 2013 PW50 2014 PW50 2015 PW50 2016 PW50