Washer for 3/4" piping with O-ring groove

thingiverse

I needed a washer to secure an O-ring on a rain water collection barrel attached to a garden hose faucet with a female 3/4" input. A threaded male adapter went through the barrel but its lip was too small for the O-ring which kept slipping and leaking around it. I placed this washer over the male adapter, slid the O-ring down into its groove, then screwed the washer through the side of a hole made in the 55-gallon barrel. Another O-ring was secured on the opposite side before screwing the garden faucet onto the assembly.