Our super-clean stainless steel pop-up gas caps fit stock and aftermarket HD type gas tanks. When installed, these caps are perfectly flush with the tank surface. To access the filler bung just push the spring-loaded pop-up center and turn 90 degrees to release, then uscrew normally (note: what looks like a paint saver ring is actually the base where the spring loaded cap recess, it is one piece with the cap and unscrews with it). Gas tanks with single filler bung will need our right side pop-up cap. Gas tanks with dual filler bung will obviously need a left and a right side pop-up cap. Gas tanks with fuel gauge unit will need our adapter and two right side pop-up caps (one for the right side and one to go inside our adapter to replace the oem fuel gauge unit): use of our adapter and pop-up cap eliminates the oem fuel gauge. Mirror polished.