ive got a hillpower one, and although they look simple there is re too them, one each and has a small flange to meet with the exhaust (one male one female) to mkae one nicely you would need to use the old cat and re wekd it to a high degree of accuracy be cause it bolts as opposed to clamps to the exhaust either soide so it needs to be totaly ligned up for the exhaust to fit correctly