Big end fits the shaft plugs on my big TX Yamaha TT600s and my Costa Rica Kawasaki KLR650, but the others are too thick for the observation plug. With a bit of careful manipulation, however, I can usually get this out as well with the big end. I plan on 'thinning' one or both of the other ends on my bench grinder, but haven't found the time. I own two, one in TX and the other in Costa Rica. Sure beats the standard screwdriver technique ... and replacing the chewed-up plugs every year or so!