Totally Rimless Back To Wall WC Pan with 4 litre flush when used with Twyford Low Volume Flush Concealed Cistern 0181/0191 Product Details Company Name Twyford Bathrooms Brand Name Avalon Model Number AV1968WH Maximum Flow Rate 4 l/min Maximum Volume 4 litres Category WC Suites Available In United Kingdom Efficiency Rating Chart Company name:Twyford Bathrooms Model:AV1968WH 4 l/min 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.