NEW AFTERMARKET 543976R91 HYDRAULIC RELIEF VALVE – 2500 PSI. REPLACES OEM PART NUMBER: 543976R91. FOR USE ON CASE INTERNATIONAL TRACTOR MODELS: Hydro 100, 766, 786, 886, 966, 986, 1066, 1086, 1466, 1468, 1486, 1566, 1568, 1586, 3388, 3588, 3788, 6388, 6588, 6788.