WATER TIGHT Rubber Grommets: in connections of DIY hydroponic systems, dutch buckets, dripping systems, siphon aquaponic systems and irrigation systems… LEAK-FREE SEAL: Donut-shaped Rubber Grommets help transfer water or nutrient solution from one reservoir to another one with tubing and barded fittings or piping and 3/4 Inch Vinyl Tubing DURABLE: periodically replace worn old ones in existing hydroponic systems to ensure air and water tight seals in your hydroponic systems 3/4 inch Donut Rubber Grommet also goes with SCH40 1/2 inch PVC pipes or pipe's outer diameter matches grommet's inner diamete The inner diameter of rubber grommet is 3/4"  the drilled hole on the bucket it fits into will need to be 1"to 1 1/8"