Makita #125355-3 Eccentric & Bearing, fits model #JS8000 Fiber Cement Shear. Replacement Eccentric Bearing assembly for Motors with a 1/2" Shaft.  Designed for cutting 1/2" fiber cement backer board & siding panel or plank. If the back of your center blade is shaped like the one in the last photo & your motor has a 1/2" shaft, this is the eccentric bearing you need.