Fits Honda Z50RD 1986, CMX250C Rebel 1985-1987 ,Verified in our NGK parts Manual, will no doubt fit other makes and models. We have a very large selections of NGK plugs for your needs. Next number is the thread reach E=19 mm or 3/4", EF=tapered seat 17.5 mm or. 708" reach, H=12.7 mm or 1/2",EH=Partial thread 19mm (3/4" total reach) &12.7mm (1/2"total thread), L=11.2 mm or 7/16", S=9.5 mm or 3/8" reach.