This cap is the for the 15qt oil drain from any automotive store or walmart. I am sure it will fit other capacity container as well. I updated the Cap in 2025 so it fits more snuggly and will not want to twist. I also added one with the Oil Logo vs the word "oil" for more general fit. To make it leak proof just apply some CA glue to the inside to seal it and print the gasket with tpu or another pliable material.