Threaded caps that effectively protect external threads where, in most cases, the liquid is inside the application that is tested under pressure. Some products are available with sealing to ensure tight closure. Soft and hard material versions are available in order to match different requirements. Shaped with outside vertical ribs to ease fitting and removal with a tool. They are recommended for multiple hydraulic applications such as: gear pumps, control valves, cylinders, steering systems; engine components: blocks, heads, power train transmissions, etc.