421-02-05-BLK 1/8" NPT to 5/16" Hose Tail - Black

Speedflow SF421-02-05-BLK | 1/8" NPT to 5/16" Hose Tail | Black | 421 Series

The Speedflow SF421-02-05-BLK is a precision-machined 1/8" NPT male to 5/16" 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 5/16" (approx. 8mm) rubber or silicone push-on hose, this compact adapter is a go-to fitting for oil pressure gauge lines, turbo oil feeds, coolant sensor connections, and small-bore hydraulic line builds in performance and motorsport vehicles.

Product Specifications

• Part Number: SF421-02-05-BLK
• NPT End: 1/8" NPT male
• Hose Tail: 5/16" (approx. 8mm) barb
• Finish: Black anodised
• Series: Speedflow 421 — NPT Hose Tails (Aluminium Barb Fittings)
• Compatible With: 1/8" NPT female ports and 5/16" ID rubber or silicone hose

Applications

The SF421-02-05-BLK is a compact, versatile adapter suited to a wide range of small-to-medium bore plumbing applications in performance builds, including:

• Oil pressure gauge and sender line connections from 1/8" NPT ported blocks and adapters
• Turbo oil feed line connections from 1/8" NPT ported centre sections
• Coolant temperature sender and bypass line connections
• Fuel pressure gauge line connections from 1/8" NPT ported regulators
• Vacuum and boost gauge line connections
• Breather and catch can line connections from 1/8" NPT ported components
• Any application requiring a 1/8" NPT male to 5/16" push-on hose interface

SF421-02-05 vs SF421-02-06 — Choosing the Right Hose Size

Both fittings share the same 1/8" NPT male port but differ in hose tail diameter. The SF421-02-05-BLK suits 5/16" (8mm) ID hose — ideal for gauge lines, sensor feeds, and small-bore turbo oil feeds. The SF421-02-06-BLK steps up to a 3/8" (10mm) hose tail for applications requiring greater flow capacity or where 3/8" hose is the build standard. Choose based on your hose ID and flow requirements.

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. Secure the hose tail with an appropriate hose clamp for pressurised applications.

Sold individually. Compatible with 1/8" NPT female ports and 5/16" ID rubber or silicone hose.