the established cushioning system from Brooks
HydroFlow® is a system of chambers sitting under the heel area of the midsole. The contained silicone-oil compound dampens the impact of the foot on the ground and offers optimal shock absorbtion and comfort. HydroFlow® is used in all Brooks shoes.
When pressure is applied to the central chamber, the liquid is displaced into the outer ducts. The central chamber decreases in volume accordingly and thereby dampens the impact. As the pressure on the chamber is decreased, the liquids retract back into it and are charged again for the next impact.