The overflow kit is essential if you are not using a rain trap as it allow the excess water in the water butt to be re-directed to a suitable drain or soak-away. The connector easily fits into the pre-drilled hole at the top of the any new Harcostar water storage system containers. It comes complete with approximately 1.5m of 2.5cm (1in) hose pipe though extra lengths are also available, see below.