Pena open Back Product Details Company Name SONAS Bathrooms Brand Name USW0399 Model Number USW0399 Maximum Volume 2.95 litres Category WC Suites Product Description Pena open Back Available In Ireland United Kingdom Efficiency Rating Chart Company name:SONAS Bathrooms Model:USW0399 2.95 litres www.uwla.eu The average flushing volume for dual flush WC Suites and Cisterns is calculated as (a + (3 × b)) ÷ 4, where a is the full flush value and b is the low flush value.