ADAPTALL MALE BSPP X FEMALE NPT C/W WASH

That washer plays a real role in keeping things tight. BSPP threads are parallel, meaning they don't seal on the thread itself the way tapered NPT threads do. The washer sits at the mating face and creates a positive seal under compression, which is what actually prevents leaks at the connection point. Without it, a parallel thread fitting like this would be prone to seeping under pressure. It's part of how the design works, not just a spare piece tucked in the bag.

It bridges a Male BSPP thread to a Female NPT thread, so it’s meant for exactly that situation where you need to connect those two standard thread types in a hydraulic setup.

Designed specifically for that purpose, this adapter makes the connection between British Standard Pipe Parallel (BSPP) and National Pipe Tapered (NPT) threads straightforward.