HS857 FAI GASKET (HEADSET) Replaces 1606912,52117800,HK5521,HK5521B,9842647FAI offer an all makes program for gaskets, oil seals and cylinder head bolts covering all main passenger car and light commercial vehicle manufacturers. Our philosophy of offering a complete gasket solution means that we always endeavor to ensure that every gasket set we catalogue will contain every gasket and seal required to finish a complete head or block rebuild. Our cylinder head bolt range is an essential addition to the gasket range, as 99% of all modern engines are fitted with “stretch” bolts which must be replaced when fitting a new head gasket. These bolts ensure that the head gasket is correctly loaded during thermal cycles, as the engines gets hot when in use and cold when at rest. If the bolts are not replaced the head gasket will fail prematurely.Our high standards mean that we always use the best materials for each part we produce, which will ensure the maximum product life span, as long as the engine manufactures thermal limits are not exceeded.