B, C , N, ER-N, ER-T, ER-X, ER-Z are all the same as far as im aware. stick a wiseco one in it. ive got a Wiseco for my TS 250 and its for all yrs. they go up to +2mm. i put a Wiseco +2 in my 185 and am very happy with it. its very quiet. make sure you have someone good doing your rebore.