Pneumatic fittings are originally made from brass. Now most of them are brass nickel plated.
This make a stronger connection compared to plastic.
Pneumission can supply the full range of fittings; push-in, crimping or thread fittings.
Series K, Flareless fitting, brass nickel plated
Thread types available: BSPP (G), BSPT(PT), NPT, Metric.
Series K, flareless fitting, brass nickel plated (PDF)