This jig precisely replicates a 4-1 and 3-1 merge collector that can be used to fit either a V band or a T3/T4 flange simply by changing the offset of the cut using the bolt on the surface. Also comes with template to mark your snd cut depending on wait size V band or flange you need to use
 
PLEASE NOTE: This jig is used for cutting TUBE and not PIPE. Pipe is commonly used in manifolds whereas tube is used in the rest of the exhaust.