Back to wall, 6/4 litre dual flush when used with the appropriate Conceala cistern Product Details Company Name Ideal Standard International NV Brand Name Alto Model Number E757301 Maximum Flow Rate 4.5 litres Maximum Volume 6/4 litres Category WC Suites Available In United Kingdom Efficiency Rating Chart Company name:Ideal Standard International NV Model:E757301 4.5 litres 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.