MP - Magmotor's Performance Line: - 5 Standard Sizes NEMA 23-68 compatible - 14 Standard Ratios - Standard backlash: 6 arc min single stage, 8 arc min 2 stage - Reduced backlash: 3 arc min single stage, 5 arc min 2 stage. NEMA - Magmotor's Economy Line: - 4 Standard Sizes: NEMA 17-42 - 8 Standard Ratios - Backlash: 12 arc min single stage, 15 arc min 2 stage.