The K&N RR-3003 is a universal-fit air filter in the 3 inch flange, 6 inch base, 5-1/4 inch top, 5 inch height configuration with a polished top. It is built for custom intake builds that run a 3-inch tube, so a buyer can match the filter to the intake without fabricating an adapter. Because the dimensions are the deciding factor, check the filter's 6 inch base and 5-1/4 inch top against your engine bay and intake clearance before ordering. Searches like "3 inch universal air filter polished top," "K&N RR-3003 3 inch flange," and "universal K&N filter custom intake 6 inch base" target the exact fitment this part serves.
The polished aluminum top gives a finished look that suits a custom intake setup, and the 5 inch height keeps the element compact under the hood. Sizing is the main reason to choose this part over a generic universal filter with unlisted dimensions: the flange, base, and top diameters all need to line up with your intake, and the figures above give you the numbers to confirm that fit. Before installation, measure your intake tube's inside diameter and confirm it matches the 3 inch flange. Fitment details can vary between applications, so confirm vehicle or motorcycle compatibility with the manufacturer before purchase.
