Spark Plug Hole Protective Cap

#9721 Spark Plug Hole Caps. Seal your Spark plug hole openings with these inexpensive tapered fit plastic caps. Prevent debris from accidentally entering ports and creating damage or mischief. Ideal for sealing for winter storage, preventing moisture from corroding internal engine parts. Also can be used to seal ports for leak testing, an important procedure that locates potential air leaks before they cause costly engine damage. Tapered fit provides positive seal for either vacuum or pressure testing, Tapers from 0.482″ to 0.526″.