A wear part includes at least one wear component made from abrasion-resistant material and an upper seal groove around a central aperture on the upper face of the wear part. The upper seal groove is adapted to receive an axially compressible seal. A spray nozzle assembly includes at least one wear part made from a hard and abrasion-resistant material and a protective housing made from a strong and resilient material and having a downstream chamber adapted to receive one or more of the wear parts in releasably trapped relationship, the downstream chamber having a wall including a post defined by a slot in the downstream chamber wall either side of the post, the post including an inwardly extending protuberance at or near its end and adapted to prevent the wear part from escaping from the downstream chamber.