Blocked Exhaust? - Excessive exhaust back pressure will decrease engine performance as well as lead to possible engine damage. This professional tester can be used to check any exhaust system and locate the restricted area. Allows pressure to be taken thru the Oxygen sensor hole or thru the exhaust pipe with the included threaded insert system. Tester includes 12mm and 18mm adapter; insert tool and inserts, screws and washers. Limited 1-year manufacturer's warranty. Made in the USA.