The SL12S Bluewater fly hook by Gamakatsu is an excellent choice for all sorts of flies for medium to large sized saltwater gamefish. This is the hook for offshore deceivers / bucktails, Trey Comb's Sea Habit type flies, and most larger streamers.
As best as we can determine, this is the same hook as the Trey Combs Big Game hook, which is also made by Gamakatsu, but distributed by Spirit River. One item of note; there is a size #1/0 available in the SL12S series, which is not available in the Trey Combs series.
(Note: Gamakatsu does not offer a 3/0 in the SL12S)
Similar hook is the TMC 600SP which runs on the large side.
Hook gap (shank to point) for 4/0 SL12S is the same size as a 1/0 TMC 600SP 1/0 -15mm
Hook length #2 25mm - hook gap (shank to point) 10mm
Hook length 1/0 - 30 mm- hook gap (point to shank) 12mm
Hook length 2/0 - 33mm- hook gap (shank to point) 13 mm
Hook length 4/0 - 40mm- hook gap (shank to point) 15 mm
Hook length 6/0 - 45mm- hook gap (shank to point) 18 mm
Hook length 8/0 - 54mm- hook gap (shank to point) 23 mm
Hook length 10/0 - 64mm- hook gap (shank to point) 28 mm