The Kraken regulator body has a groove for an O-ring seal and does not use a cork gasket (between the body and can) as does the original USD/Voit body. The groove is in the regulator body, not the ABS plastic can. You will need to use a (original type) rubber/cork gasket with the Phoenix converted USD/Voit regulator body with Kraken cans. You can see the large O-ring in this photo that seals the Kraken lower can to the regulator brass body:
Some Krakens in the field have been modified with a more aggressive flow vane in the DSV to allow hotter tuning and an ambient diaphragm outward (over) travel positive stop to prevent the sticking to the exhaust mushroom valve that some have experienced
.