Use a goof plug to plug holes in 1/2" poly tube or closes the end of 1/4" micro tube. This goof plug has different sizes on each end. Use the small side to plug the end of 1/4 line or 1/4" holes in 1/2" poly tube. The large side can be used to give an extra tight fit for 1/4" holes or anytime the smaller side does not seal properly.