The 2 types · side-by-side
Distributor-facing reading. Each row gives best-for, key trade-off, capacity, price band, and how many of SPC's tier slots carry an option at that product type.
Product type
Best for
Key trade-off
Typical capacity
Price band
Brands SPC carries
Instrumentation SS Tube Fitting Double-ferrule · B31.3 · Swagelok-compatible geometry
Analyzers, sample lines, high-purity, hazardous-gas.Instrument-air headers, sample lines, gauge and transmitter connections in oil & gas, petrochemical, semiconductor, and lab service. Double-ferrule design grips and seals on the tube OD; reusable across many re-makes. Dimensionally compatible with Swagelok and Parker A-LOK / CPI standards.
Different family from push-to-connectNot interchangeable with pneumatic PTC fittings — different mechanism, different installation, different code basis (ASME B31.3 / B31.1). Engineered around the re-make: properly installed, a 316 SS fitting will re-seal ten times or more on the same ferrules.
1/8"-2" + 3-50 mm metric
316 SS standard · 304 / brass on lighter service
316 SS standard · 304 / brass on lighter service
$$ – $$$
1 / 5 · DK-LOK only
DOT Air Brake Fitting Commercial vehicle · 49 CFR 393/571 · FMVSS 121
Trucks, trailers, buses, heavy equipment.Commercial-vehicle air-brake systems — service, emergency, parking, and auxiliary brake circuits on any vehicle with GVWR above 10,000 lb. Fleet maintenance, trailer manufacturers, truck OEM. Designed for SAE J844 DOT nylon air brake tubing.
Regulatory category, not an upgrade<b>Industrial machine-pneumatic fittings are not legal substitutes in a DOT-regulated brake circuit.</b> A non-DOT fitting in a brake circuit is an Out-of-Service violation at roadside inspection and an unbounded liability if a crash results. No exceptions, no substitutions.
1/4" · 3/8" · 1/2" · 5/8" tubing OD
Push-to-connect or compression · SAE J844 nylon
Push-to-connect or compression · SAE J844 nylon
$$
1 / 5 · Alkon only
Reading the brand bench column — the bar shows how many of SPC's tier slots carry an option at that product type. Both specialty families run a single brand deep because the specs are narrow and code-driven: DK-LOK on the instrumentation double-ferrule side, Alkon on the DOT air-brake side. These are regulatory categories, not push-to-connect tiers — the code sets the spec, and there is no industrial substitute.