The NATO strap takes its name from the NATO Stock Number under which a British Ministry of Defence webbing strap was catalogued, with the spec drawn up in 1973. Soldiers requisitioned it on a G1098 form, which is why you'll also hear it called a G10 strap. The original spec was strict and a little dull: nylon in Admiralty Grey only, 20mm wide, with a chrome-plated brass buckle and keepers. What separates it from a plain nylon band is the double-pass construction. A second, shorter length of nylon runs beneath the watch and through the keepers, so even if one spring bar lets go, the watch head stays put. Historic production came from Phoenix Straps in Cardiff.
Real-world examples span a wide price spread. Crown & Buckle's nylon NATOs start around $16 at the entry end and climb to roughly $38 for the Supreme and matte lines, with a tight weave and a deep color range that punches well above the money. At the other end, Omega sells polyamide NATOs for the Seamaster in the region of $210, with some striped versions made from recycled fishing net and finished with an engraved Seamaster keeper. A cinema footnote worth knowing: Sean Connery's striped strap in Goldfinger (1964) was a single-pass band and technically pre-NATO, since the MoD spec only arrived in 1973. Blu-ray restoration revealed the stripes as navy, olive and red. Daniel Craig's fabric-strapped Seamaster is a deliberate nod back to it.
When you're buying, a few practical things matter. Weave matters most: a medium-firm, tightly woven nylon lies flatter under the watch than a floppy, ultra-soft one. Look for stainless steel hardware and heat-sealed, sealed-edge ends that won't fray. Measure your lug width carefully, with 20mm and 22mm the most common. Remember that the under-watch layer lifts the case slightly, so a thick diver can ride taller than you'd expect. A NATO suits anyone who wants a tough, swap-it-in-seconds everyday strap and doesn't mind a casual look that won't read as dressy as a bracelet.
Don't conflate the sub-types. A RAF or single-pass strap drops that second under-watch layer for a single band that sits the case closer to the lugs. A Zulu uses heavier, rounded hardware for a chunkier feel. Elastic Marine Nationale straps like Erika's Originals MN, around €90, are a separate family that stretches and adjusts but isn't a true double-pass NATO. If you want belt-and-braces security and fast changes, the real NATO is the one; if you want a slimmer profile, go single-pass.