Quality fittings machined straight from bar stock. NPT thread is the American version of BSP thread. They are non metric threads but still industry standard. The barb (non-threaded) ends are meant to take the appropriate size fuel hose - just push on. Some people will use a drop of thread locker or special pipe compound. The threaded ends will be ok with a little thread tape, but some people say not to use anything at all. If the finished joint does not "weep" fuel, leave it alone. If it weeps, start again with tape and joint compound. Always use a hose clamp on the barb ends.