Vintage Double Hose

Guys,
What type of O-rings do they use for the Scuba tank? I know there are 3 types,
Nitrile(Black), Viton(Green) and HNBR (Brown).I am assuming that the size is Standard not metric.
Thanks,
Boyet

BUNA N - Nitrile is the most common.

Viton is the most common for Nitrox applications.

O-rings come in all colors ....I have BUNA O-rings in red, yellow, shades of blue and green also different durometers. (hardness)

Viton is generally brown but I have seen black, blue, green, tan and white.

Don't go by color alone.

Google search will provide hours of reading enjoyment....Just type in Scuba and O-ring types and you can read for hours.