mike_s
Contributor
Only thing I could add to Mike's post, is that Faber FX are actually better than Worthington's on that score.
here they all are in a somewhat easy to read table/chart ( for comparison).
(weight shown on all weight values is in pounds).
I also included the AL80 since that is the standard tank a lot of divers use and that way it could be compared also.
[table 0 0 3] Tank | PSI | Empty wt. | Buoyancy Empt | Buoyancy Full
Faber HP-100| 3180 +10% | 38.7 | -7.26 | -14.76
Faber FX-100| 3442 | 34.3 | -0.59 | -8.41
Worthington X7-100| 3442 | 33 | -2.5 | -10
Luxfer 80 (77.4cf) | 3000 | 31.38| 4.4 | -1.4
[/table]
The Faber FX is better than the worthington on being negative at -8.41 pounds verses -10 pounds. On a set doubles, this would be a change of just over 3 pounds, which isn't much.
However, for a single tank, the negative 10 pounds might be desired for a non-steel-backplate diver as it allows the diver to take some weight off their waistbelt.
Depending on what suit I've got on, with the Fabers I can dive with no lead weight in freshwater, and barely any lead in salt. With the Worthington I doubt I'd need any in salt water (unless I had a thicker suit on). So all depends on the divers needs for what type of dive they are going to do, and in what conditions.
However, with the Faber HP100 at negative -14.76, thats a lot of negative weight to overcome. Especially with doubles (-29 pounds) and a 6 pound steel back plate. (in my opinion).