Can be made to work, but need improvement.
Main thing is this fixed the problem of a corroded out aluminum fuel tank filler neck in a 1980s Bayliner fishing boat.
Rubber gasket that comes with it is junk. Really needs rubber gasket with cloth fibers in it to keep the gasket from just swelling out when under pressure. Also needs same rubber with cloth fibers gaskets for each bolt head. Made new gaskets with rubber/paper gasket material and replaced the all too small metal washers with nylon washers with bigger OD.
Would be a better product if the bolt pattern was moved inward about 1/4" (6mm) to give a little wider outer gasket sealing area, or perhaps making the OD of the part that much wider.
Rather pay $5.00 more for a properly made part than to spend two tries to get the part to seal up.