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

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

The Speedflow SF421-06-06-BLK is a precision-machined 3/8" NPT male to 3/8" hose tail adapter in black anodised finish, part of the Speedflow 421 series NPT hose tail range. Connecting 3/8" NPT ported components directly to 3/8" (approx. 10mm) rubber or silicone push-on hose, this adapter is a staple fitting for coolant, oil, fuel, and power steering line builds in performance and motorsport vehicles where port and hose sizes are matched.

Product Specifications

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

Applications

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

• Engine coolant line connections from 3/8" NPT ported thermostat housings, blocks, and heads
• Oil feed and return line connections from 3/8" NPT ported oil coolers and sandwich plates
• Power steering reservoir and pump line connections
• Fuel line connections from 3/8" NPT ported fuel regulators and filters
• Heater hose and bypass line connections to 3/8" NPT ported fittings
• Any application requiring a matched 3/8" NPT male to 3/8" push-on hose interface

SF421-06-06 vs SF421-06-08 — Matched vs Stepped Hose Tail

Both fittings share the same 3/8" NPT male port but differ in hose tail size. The SF421-06-06-BLK features a matched 3/8" hose tail for direct connection to 3/8" ID hose, while the SF421-06-08-BLK steps up to a 1/2" hose tail for higher-flow applications. Choose the SF421-06-06-BLK when your hose ID matches the port size, and the SF421-06-08-BLK when you need to step up to larger hose for increased flow capacity.

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 — NPT threads can crack cast components if over-torqued. Secure the hose tail with an appropriate hose clamp for pressurised coolant and oil applications.

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