I use the NGK red rubber ones they still use the nipple on the top of the plug, they seem to grip the plug all the way down. They do a maroon Bakelite one that you have to remove the nipple. Personal choice but the Nippon Denso plugs I use don't have removable nipples, one less thing to drop off. I went through a phase of breaking down to find the nipple in the cap even with a dab of locktight