421-02-03-BLK 1/8" NPT to 3/16" Hose Tail - Black

Speedflow SF421-02-03-BLK | 1/8" NPT to 3/16" Hose Tail | Black | 421 Series

The Speedflow SF421-02-03-BLK is a precision-machined 1/8" NPT male to 3/16" hose tail adapter in black anodised finish, part of the Speedflow 421 series NPT hose tail range. The smallest hose tail diameter in the 1/8" NPT family, this compact adapter connects 1/8" NPT ported components to 3/16" (approx. 5mm) rubber or silicone push-on hose — making it the ideal choice for oil pressure gauge lines, vacuum lines, boost reference lines, and other small-bore sensor and instrument connections in performance and motorsport builds.

Product Specifications

• Part Number: SF421-02-03-BLK
• NPT End: 1/8" NPT male
• Hose Tail: 3/16" (approx. 5mm) barb
• Finish: Black anodised
• Series: Speedflow 421 — NPT Hose Tails (Aluminium Barb Fittings)
• Compatible With: 1/8" NPT female ports and 3/16" ID rubber or silicone hose

Applications

The SF421-02-03-BLK is the go-to adapter for small-bore instrument and sensor line connections in performance builds, including:

• Oil pressure gauge line connections from 1/8" NPT ported blocks, adapters, and sandwich plates
• Boost and vacuum gauge reference line connections
• Fuel pressure gauge line connections from 1/8" NPT ported regulators
• Turbo boost reference and wastegate actuator line connections
• EGT and sensor reference line connections
• Any application requiring a 1/8" NPT male to 3/16" small-bore push-on hose interface

421 Series 1/8" NPT Hose Tail Range — Choosing the Right Size

The Speedflow 421 series offers three hose tail sizes for the 1/8" NPT port, allowing you to match the hose tail to your specific hose ID and flow requirements:

• SF421-02-03-BLK — 3/16" hose tail: ideal for gauge lines, vacuum, and boost reference (this listing)
• SF421-02-05-BLK — 5/16" hose tail: suits oil pressure feeds, small turbo oil feeds, and sensor lines
• SF421-02-06-BLK — 3/8" hose tail: for higher-flow applications or where 3/8" hose is the build standard

NPT Installation Note

NPT fittings use a tapered thread that seals via thread interference. Always apply appropriate thread sealant or PTFE tape to the NPT male threads during installation. Do not overtighten. For low-pressure gauge and vacuum lines, a hose clamp may not be required, but is recommended for any pressurised application.

Sold individually. Compatible with 1/8" NPT female ports and 3/16" ID rubber or silicone hose.