White 18" x 18" x 1.5" extended flushpipe suitable for low level and ducted installations. Allows water to go from cistern to the pan when the cistern is flushed. Extended flushpipe Suitable for ducted installations Can be cut down to suit installation Suitable for low level applications. Wirquin White 457. 2 mm x 457. 2 mm x 38. 1 mm extended flushpipe is suitable for low-level and ducted installations. It allows water to go from the cistern to the pan when the cistern is flushed.