A tapered woven nylon exterior with engraved rivets, quick detach spring bars, and soft underliner. Features both ground and air (Army and Air Force) design elements. PATTERN/ PAIRING: The AAF (Army Airforce) Sea Grey 637 watch strap features a blued medium grey exterior with a neutral grey underliner and reinforced hole settings. Sea Grey 637 is based on a high-altitude maritime grey used on mid to late WWII aircraft. With an appearance between blue and grey, Sea Grey 637 makes for a unique neutral pairing with Dive and Pilot pieces as well as with monotone dial designs. LAYOUT:A 2 piece layout specially tailored to accommodate a wide range of wearer's wrist, and case lug-to-lug sizes. Equipped with vintage aviation features including a distinctive 6mm engraved rivet, bead blasted aviator roller buckle and a slightly tapered profile leading from a 20mm start to an 18mm buckle. INSTALLATION Outfitted with quick detach spring bars for fast and simple installation.