These four rolls of underlay by Hornby are designed to be placed under Hornby railway track. Each roll measures approximately 4880mm. The underlay fits snugly under a single track, and even comes with indentations where there are sleepers. The underlay is incredibly flexible as it can lie flat, or curve, to match the chosen track layout. Trains move more smoothly when underlay is used, plus it helps quieten any vibrations.