NPT fittings can be confusing because the nomenclature does not refer to the thread size. This page will help you identify which NPT fitting size you have.
1/4 to 7/16-24 Long Version Inverted Flare Tube Nut, Steel
BSP Male to BSP Male Adapter - Pegasus Auto Racing Supplies
A close nipple is the same as a male-to-male adapter, but without the center hex. This brass fitting has male 1/4 NPT threads on each end.
Close Nipple, 1/4 NPT Brass
Male NPT Pipe to Female AN Swivel Adapter, Stainless Steel - Pegasus Auto Racing Supplies
These AN932-style fittings conform to JIC and SAE specifications. Each plug is constructed of anodized aluminum and accepts a standard SAE male hex
AN932 Allen Head Pipe Plug
Why You Should Avoid NPT Fittings Hose Assembly Tips, 45% OFF
Quick-Disconnect Socket to 3/8 NPT Male, 3000 Series
Male 14 x 1.5mm Metric Concave Seat to 6AN Male, Steel - Pegasus Auto Racing Supplies
Pegasus HJ28, 28mm (1 1/8 inch) Pegasus Pro Design Aluminum Hose Joiner : Automotive
AN921 O-Ring Boss Adapter - 90' Elbow
AN816 Male NPT Pipe to Male AN Adapter, Black Aluminum - Pegasus Auto Racing Supplies
4AN/42 degree Inverted Flare 1/2-20 Brake Adapter-Short
NPT Fittings: Background and Use - Pegasus Auto Racing Supplies
The Jiffy-Tite 2000 series will flow 1.75 GPM with a 5psi inlet pressure through a mated pair of valved fittings attached to 3 feet of -6 hose. Flow
Quick-Disconnect Plug to 1/4 NPT Male, Non-Valved, 2k Series