I believe they just put new pipes on them. Seems to be the same length a the original. When tooling all they had to do was leave out the curling step.
While Bisson is a good product, I personally have not like the shape of most of their products. I typically go with Slimline due to their compact shape. DA says to buy the $99 Slimline and drill a hole and install a nipple between the head and the can for smoke. No need for the preheater element. Works well.