Abstract: A fluid tight sliding clasp open ended or separable continuous fastener has two parts each comprising a row of fastening elements secured to a strip of impervious flexible material and a slider operable to close at least one end of the fastener, the elements of the two rows creating a seal against fluid pressure acting transversely of the fastener. Each part has adjacent the end to be closed additional sealing means on that face of the respective strip which, in use, forms the inside face, the additional sealing means of each part being preshaped so that when said one end of the fastener is closed they lie in edge to edge contact and are under compression whereby a fluid tight seal is obtained therebetween for resisting, in use, fluid pressure acting longitudinally of the fastener at said one end of the fastener. The fastener is particularly designed for protective suits.