Dumb non-box person question... Are 3 litre cylinders "better" than 2 litre cylinders? I appreciate that you actually only use the diluent for filling the loop on the bottom; once they're 'filled' then you don't need the diluent except for problems. Similarly the O2 is only required to replace the metabolised O2 (about 1 litre/min???). So therefore there's plenty of gas in 2 litres. However, if there's problems, wouldn't having additional gas be a benefit? For instance each time you flush the loop you'd need a fair amount? (Excuse my ignorance, not dived one nor taken any courses) Also if you're doing multiple dives, wouldn't 2 litre cylinders mean that you'd need to fill them in between dives? Are 2 litre tins that much lighter than 3 litre tins? This thought train was brought on by looking at the Red Bare which only has space for 2 litre tins unless modifications are made (the stand needs to be extended and there's only enough space for 'dumpy' 3 litre tins).