421-02-04-BLK 1/8" NPT to 1/4" Hose Tail - Black

Speedflow SF421-02-04-BLK | 1/8" NPT to 1/4" Hose Tail | Black | 421 Series

The Speedflow SF421-02-04-BLK is a precision-machined 1/8" NPT male to 1/4" hose tail adapter in black anodised finish, part of the Speedflow 421 series NPT hose tail range. Connecting 1/8" NPT ported components to standard 1/4" (approx. 6mm) rubber or silicone push-on hose, this adapter sits between the 3/16" and 5/16" variants in the 1/8" NPT hose tail family — suited to oil pressure gauge lines, vacuum and boost reference lines, and small-bore sensor connections in performance and motorsport builds.

Product Specifications

• Part Number: SF421-02-04-BLK
• NPT End: 1/8" NPT male
• Hose Tail: 1/4" (approx. 6mm) barb
• Finish: Black anodised
• Series: Speedflow 421 — NPT Hose Tails (Aluminium Barb Fittings)
• Compatible With: 1/8" NPT female ports and 1/4" ID rubber or silicone hose

Applications

The SF421-02-04-BLK is a compact, versatile adapter suited to small-bore instrument and sensor line connections in performance builds, including:

• Oil pressure gauge and sender line connections from 1/8" NPT ported blocks and adapters
• 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
• Coolant temperature sender line connections
• Any application requiring a 1/8" NPT male to 1/4" push-on hose interface

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

The Speedflow 421 series offers four 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
• SF421-02-04-BLK — 1/4" hose tail: suits gauge lines and small sensor feeds (this listing)
• SF421-02-05-BLK — 5/16" hose tail: suits oil pressure feeds and small turbo oil feeds
• 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 1/4" ID rubber or silicone hose.