Our Series 8555-H Metric MM Hollow Hex Plug adapters, made from durable carbon steel, are essential components designed to seal off open ports in hydraulic and fluid systems. These plugs feature a hollow hex design, making them easy to install or remove using standard tools, offering convenience in tight spaces. The Metric MM (Metric Male) thread ensures a secure connection that creates a tight seal when installed, preventing leaks and maintaining system integrity. Ideal for systems using metric thread connections, these hollow hex plugs provide a reliable and cost-effective solution for closing unused ports. Built to withstand high-pressure environments, the Series 8555-H adapters are a trusted choice for professionals looking for durable, long-lasting sealing solutions in fluid power systems.