K&N Individual Round Style Stacks for â€œEarly Typeâ€ Fuel Injectors (Single Stacks) for Chevrolet, Etc. - Filters designed to fit with cut velocity stacks, or straight pieces of exhaust tubing. Rubber filter bases come with molded in velocity stack type radius and step, for smooth bore down from element to tube. Each filter has a rubber top with a stamped K&N logo. As with all K&N air filters, these are washable and reusable. Simply use K&N oil and cleaner to service your filter.