Off road or race silencers increase performance but don’t meet the noise and emission standards in most counties. It is a popular modification to fit an illegal race exhaust to a motorcycle for a number of reasons; lighter weight, greater noise and more power seem to be the most popular. Of course vanity plays a part in this also which has led to many exhaust manufacturers making extremely stylish carbon fibre and titanium cans in a variety of shapes and sizes. The baffling in a road legal can is usually very complicated and adds greatly to the overall weight but recently several companies have designed a removable baffle that can turn a race can into a nice quiet road can that passes the required tests to be given type approval. The benefits of this are lighter weight, more choice and no legal issues. Recent changes in the rules for MOT now let the tester pass any silencer they feel is quiet enough regardless if it has an E mark or BS stamp.