Never heard of these, how long have they been around? https://sites.google.com/site/westernwashingtonwelding/
beats me. but Jimm Hobbs makes -authorized- denco reproductions that are super nice. these look like some guy just sort of copied them. im sure they are ok, but id go with jims pipes. i can confirm they are exact copies but with much better build quality.
Id like to see somebody reproduce the Denco RD pipes. those worked really well. . Or see John get some pro-flo pipes back into production.