Product Specifications
Diameter: 25mm (1 inch) internal diameter (ID); some sources may refer to the slightly larger external diameter.
Length: 25-metre coil..
Color: Typically black, which helps to discourage algae growth inside the hose.
Features: Corrugated for strength and flexibility, and often UV-resistant. The inside wall is often smooth to maximize flow rates and minimize friction loss. 
 
Proven to be a useful product when longer overflow hose needed for waste 7 traps.