If you don't have access to service kits, the temptation to crosswalk o-rings is strong. But Scubapro, Aqualung and Apeks use a lot of "non-standard" sizes, at least for US folks used to AS568 standards. There are at least a half dozen threads here on SB that touch on Apeks sizing. I won't list them, because my concern has been the sheer number of small errors.
On top of that, Apeks has recently adopted the "RG" numbering system used by their 1997 purchaser/parent, Aqualung.
And worse, the RG number listed on the new schematic is the number for the "10-pack" of o-rings, which doesn't match the number on the Service Kit card.
You want more? The sizing diagram, complete with a ruler that tells you exactly how large to print the page, STILL doesn't exactly match the actual orings, when you're sorting through the kit.
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The attached spreadsheet is the result of micrometer measurements of every o-ring in several
new service kits. I've included my estimate of o-ring durometer, despite the "common knowledge" that Apeks uses all EPDM duro 80. That's clearly not true if you feel the DIN o-ring, but nevermind.
Hopefully this will show where you can use AS568 o-rings, and where you might need to go searching for a metric, a British Standard metric (BS4518), a British Standard 1806 o-ring, or even a few ISO 3601 parts. ALL listed measurements are in millimeters.
I don't claim that this is definitive. This is definitely a "USE AT YOUR OWN RISK" product, especially for dynamic seals. But it's an attempt to clean up some of the gaps I've noted in existing spreadsheets, where the listed substitution just doesn't match the kit closely enough for my comfort as a DIY'er. Enjoy!
