and 34 are held in the openings 20 by a connector mechanically connected to the fitting 32 and 34 to hold the fittings 32 and 34 in engagement with the interior of the first tank 18 about the openings 20 the invention is illustrated by two different embodiments of the fitting and connector in the first embodiment 32 of the fitting the fitting 32 extends through the opening 20 in the first tank 18 and the connector 35 surrounds and mechanically connects to the fitting 32 on the exterior of the metal tank 18 the fitting 32 includes an annular groove 36 and the connector 35 is disposed in the annular groove 36 more specifically the connector 35 comprises a pair of complimentary retention rings 38 disposed in the groove 36 and having ends abutting one another with mechanical connections 40 42 connecting the abutting ends thereof the connections 40 42 comprise hooks 40 on one of the rings 38 that are crimped around radial tabs on the other of the rings 38 the rings 38 may be identical with one of hooks 40 on one abutting end and one of the tabs 42 on the opposite abutting end the braze clad is disposed on the interior surface of the connector 35 to engage the annular groove 36 once in the brazing oven molten braze clad flows into the interface 44 between the fitting 32 and the interior of the.