VALVE SEAT GRINDER STONES + HOLDER / CARRIER + PILOTS + DRIVE BALL HIGH PERFORMANCE STONES SOUND LESS ROTATION HOLDER STONE SIZES :- 4x 2", , 1.3/4" , 1.1/2" , 1.3/8" Pliots 2x 11/32", 5/16" Stone holder 2x 1702 BB Style Star Drive Ball + Shaft 2x STONE & Holder Thread THREAD - 11/16" x 16 tpi