The BR-M8120 is a hydraulic disc brake caliper. The BR-M8120 has 4 pistons which are quick to react. In addition, it reduces brake rotor wobbling noise & increase braking power by 10% in comparison to the M8000 design. The high braking power instils greater downhill confidence & control. Shimano recommends M8100 XT hydraulic break components to be paired with this product.