Bulkhead heads are what's in a "fittings relocation kit." Using a bulkhead fitting requires access to the inside of the tank to insert the fitting in the new hole so that the hose barb is on the outside of the tank. Not a major problem if there's an inspection
port in the tank, AND you can reach the new hole from it, but definitely a major problem if there is no useable access to the inside of the tank. Less problematic is the need for two gaskets--one under the flange on the inside of the tank, the other under the nut on the outside of the tank. The Uniseal eliminates the need for either...and for LOT less $$ too!
Btw...Around midnight my time last night I emailed assieglobe re the instructions. In what had to be the fastest response in the history
of the need they put up an "instructions" tab and replied to me saying they'd done it...time stamped 12:47am....on a SUNDAY night! Now THAT's customer service!