Strap Material is one of the most practical axes along which watches differ, defining what the band connecting the watch to your wrist is actually made of. The same case can read as an elegant dress watch on leather, a serious dive tool on FKM rubber, or an easy weekend piece on woven nylon. Leather and metal bracelets dominated for decades, until the British Ministry of Defence issued its nylon NATO strap in 1973, nicknamed the G10 after the G1098 requisition form, cementing a military-rooted third path. Today the choice is a deliberate trade-off between comfort, water resistance, formality and upkeep.
Real examples sharpen the distinctions. Rolex's Oysterflex bracelet wraps a titanium and nickel alloy metal blade in black elastomer, bringing rubber into the luxury tier on the Daytona, Yacht-Master and Sky-Dweller. The Tudor Pelagos ships with a black rubber strap alongside its titanium bracelet, and on the rubber side FKM resists heat, oils and UV while lasting 5 to 10 years or more, whereas cheap silicone tends to crack or get sticky in 2 to 3 years. In the aftermarket, Erika's Originals elastic MN straps run around $90, Delugs alligator signature straps about $205 with entry leather from roughly $95, while Omega charges around $210 for its own polyamide NATO.
When choosing, be honest about how you actually live with a watch. For the office and formal settings, calfskin or alligator leather gives the most natural stance, though daily wear chews through calfskin in 1 to 2 years and alligator in roughly 3 to 5. For a life around water, sweat and heat, FKM rubber or a nylon NATO makes far more sense, since both dry fast, wipe clean and cost little to replace. A metal bracelet is the most durable and formal everyday option, but it can scratch and the links can stretch over time. Buying alligator, look for broad symmetric tiles; alligator-embossed calfskin is cheaper and sometimes passed off as the real thing.
The material axis rewards a closer look at sub-types. Within leather, calfskin, shell cordovan and exotic alligator each patina and dress differently; within rubber, vulcanised, silicone and premium FKM span a real quality gap. Hybrid straps laminate a leather or sailcloth face onto a rubber core for looks plus resilience. The good news is that most modern watches let you swap material in minutes, so a single watch can take on several characters depending on the day.