The Siamp 99T 3/8" Brass Inlet Valve (Manufacturer's Part Number: 30992210) is a popular, high-quality telescopic bottom-entry fill valve known for its quiet operation and durability in both professional and DIY settings. 
Key Features and Specifications
3/8" Brass Thread: The key feature is the 3/8-inch BSP (British Standard Pipe) solid brass tail connection. This "European small size" thread is crucial for certain imported WC suites and prevents common installation problems like cross-threading, offering a more secure and robust fitting than plastic alternatives.
Telescopic and Adjustable: The valve's height is fully adjustable (telescopic) from approximately 240mm to 344mm (around 9.4 to 13.5 inches), making it highly versatile for fitting into a wide range of cistern heights, whether surface-mounted or concealed.
Quiet and Efficient: It features a quiet, "hydraulic closure" mechanism designed to prevent water hammer shock (the banging sound in pipes) when the water shuts off.
Wide Pressure Compatibility: The 99T valve is suitable for both high- and low-pressure water systems, with an operating range typically from 0.1 bar up to 10 bar, ensuring consistent performance across different plumbing systems.
Anti-Backflow Function: It incorporates an anti-siphon design to prevent the contamination of the fresh water supply, ensuring it is compliant with water regulations.
Easy Maintenance: The design allows for easy adjustment of the water level within the cistern.
Guarantee: The product often comes with a generous 10-year guarantee, reflecting its build quality and reliability. 
The Siamp 99T is a professional-grade valve that balances excellent performance with durable materials, making it a reliable choice for long-term use.