N82M is the standard needle that came from the factory. N82R is the one that Destry and some of the desert racers used to run as an optional one. Not too sure on the dimensions but Kawasaki still lists the following: KX500
16009 16009-1578 NEEDLE-JET,N82K 1 (OPTION)
16009A 16009-1579 NEEDLE-JET,N82L 1 (OPTION)
16009B 16009-1580 NEEDLE-JET,N82M 1
16009C 16009-1581 NEEDLE-JET,N82N 1 (OPTION)
16009D 16009-1582 NEEDLE-JET,N82P 1 (OPTION)
16009E 16009-1609 NEEDLE-JET,N89Z 1 (OPTION)
16009F 16009-1610 NEEDLE-JET,N89A 1 (OPTION)
16009G 16009-1611 NEEDLE-JET,N89B 1 (OPTION)
16009H 16009-1612 NEEDLE-JET,N89C 1 (OPTION)
16009I 16009-1613 NEEDLE-JET,N89D 1 (OPTION)