Will, I used to use these thumbnail SPG's as well, but no longer do so because
they are useless in 
zero visibility.  This may not apply to most persons, but even in faceplate vis
a full size gauge 
may be held against the mask in front of one eye while shining your light into
your other eye 
(which is shut), and be read without difficulty.  I have also heard that the
thumbnail gauges have 
a tendency to get stuck, however I can not confirm or deny this.

-Sean


On Tue, 27 Jan 1998 10:41:56 -0500 (EST), William M. Smithers wrote:

>I've been using these tiny SPG's that are built
>into a 1/2" nut package that's like 3/4" high.  They screw directly into 
>the HP port, are low-profile, with a tiny (but fairly accurate) guage
>inside, that clearly shows red at 500PSI, yellow at 1000,
>and green above.  I rig the deco bottle so that the SPG "nut"
>is pointing up, and it's fairly easy to read.  
>
>And the things are indestructible - I've dropped an AL80 
>deco bottle rigged this way where it fell directly on the 
>SPG from several feet, and it keeps on going.
>
>For deco bottles, they're perfect, because all I really want is
>a ball-park estimate of how much gas is available - I've
>already planned for consumption and reserves, so who cares
>if I know whether I've got 1500 or 1625 PSI.
>
>They run about $30 apiece at my local high-markup dive shop.
>
>-Will

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