421-06-08-BLK 3/8" NPT to 1/2" hose tail

Speedflow SF421-06-08-BLK | 3/8" NPT to 1/2" Hose Tail | Black | 421 Series

The Speedflow SF421-06-08-BLK is a precision-machined 3/8" NPT male to 1/2" hose tail adapter in black anodised finish, part of the Speedflow 421 series NPT hose tail range. Designed for high-flow applications, this adapter connects 3/8" NPT ported components to standard 1/2" (approx. 13mm) rubber or silicone push-on hose — making it an essential fitting for coolant, oil, fuel, and power steering line builds in performance and motorsport vehicles.

Product Specifications

• Part Number: SF421-06-08-BLK
• NPT End: 3/8" NPT male
• Hose Tail: 1/2" (approx. 13mm) barb
• Finish: Black anodised
• Series: Speedflow 421 — NPT Hose Tails (Aluminium Barb Fittings)
• Compatible With: 3/8" NPT female ports and 1/2" ID rubber or silicone hose

Applications

The SF421-06-08-BLK is a 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 connections to 3/8" NPT ported fittings
• Any high-flow application requiring a 3/8" NPT male to 1/2" push-on hose interface

421 Series — NPT Hose Tails

The Speedflow 421 series covers a comprehensive range of NPT male to hose tail sizes in black anodised aluminium, from small-bore 1/16" NPT gauge line adapters through to large-bore 3/8" NPT high-flow fittings like the SF421-06-08-BLK. The 3/8" NPT to 1/2" hose tail combination is one of the most commonly used in coolant and oil system plumbing, providing ample flow capacity for engine cooling and lubrication applications. The barbed hose tail grips securely to push-on hose for a reliable connection.

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 1/2" ID rubber or silicone hose.