I used this one, https://www.spectreperformance.com/accessories/17385-o-ring-oil-cap-push I used a hole saw to drill the 1 1/4" hole. The above simply pushes in and pulls out. You can also use an additional breather. Glue the grommet to the 1 1/4" hole in the cover, then the breather pushes in and pulls out.