421-04-06-BLK 1/4" NPT to 3/8" Hose Tail - Black

Speedflow SF421-04-06-BLK | 1/4" NPT to 3/8" Hose Tail | Black | 421 Series

The Speedflow SF421-04-06-BLK is a precision-machined 1/4" NPT male to 3/8" hose tail adapter in black anodised finish, part of the Speedflow 421 series NPT hose tail range. This stepped adapter connects 1/4" NPT ported components to the larger 3/8" (approx. 10mm) rubber or silicone push-on hose, making it ideal for applications where increased hose flow capacity is needed beyond what a matched 1/4" hose tail would provide.

Product Specifications

• Part Number: SF421-04-06-BLK
• NPT End: 1/4" NPT male
• Hose Tail: 3/8" (approx. 10mm) barb
• Finish: Black anodised
• Series: Speedflow 421 — NPT Hose Tails (Aluminium Barb Fittings)
• Compatible With: 1/4" NPT female ports and 3/8" ID rubber or silicone hose

Applications

The SF421-04-06-BLK is a versatile stepped hose tail adapter suited to a wide range of performance plumbing applications, including:

• Oil pressure and temperature sender connections stepping up to 3/8" hose
• Coolant line connections from 1/4" NPT ported thermostat housings and blocks
• Oil feed line connections from 1/4" NPT ported oil coolers and sandwich plates
• Fuel line connections from 1/4" NPT ported regulators and filters
• Turbo oil feed line connections stepping up to larger hose diameter
• Any application requiring a 1/4" NPT male to 3/8" push-on hose step-up interface

1/4" NPT — The Most Common Performance Port Size

The 1/4" NPT thread is the most widely used NPT port size across aftermarket performance components — found on oil pressure senders, temperature sensors, oil cooler sandwich plates, fuel regulators, turbo oil feeds, and countless other fittings. The SF421-04-06-BLK steps up from this common 1/4" NPT port to a 3/8" hose tail, providing increased flow capacity compared to a matched 1/4" hose tail — useful when routing to a larger hose section or when minimising flow restriction is a priority.

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 1/4" NPT female ports and 3/8" ID rubber or silicone hose.