Watch strap
A watch strap, watch band, watch bracelet or watch belt is a bracelet that straps a wrist watch onto the wrist. Watch straps may be made of leather, plastic, rubber, cloth, or metal, sometimes in combination. It can be regarded as a fashion item, serving both a utilitarian and decorative function. Some metal watch straps may be plated with, or even in rare cases made of, precious metals. Watch straps may close with a buckle or a folding clasp. Expanding watch straps are designed to expand elastically, often by the use of metal springs in a segmented design , and may be slipped on like a bracelet. Attachment points for the strap to the watch are largely standardized, with a spring bar (a spring-loaded double-ended pin) used to anchor the watch strap to holes in a bracket that is integral to the watch case, allowing worn watch straps to be replaced or swapped with new straps for fashion purposes. Metal watch straps are typically stainless steel. The most common metal watch strap styles are the folded link, pushpin, and screw-in styles. Both metal watch cases and watch straps incorporating metal parts can sometimes cause contact dermatitis  in susceptible individuals. Special anti-allergy watch straps, like a NATO style watch strap, which shield the skin from exposure to metal parts, are available for sufferers of this type of dermatitis. Specialist expanding watch straps exist for use with diving watches. With increasing depth and rising water pressure the (sleeved) wrist of a diver is exposed to compression effects that have a shrinking effect on the wrist circumference. Many watch straps intended for diving watches have rippled or vented sections near the attachment points on the watch case to facilitate the required flexibility to strap the watch exaggeratedly tight  for normal wear at the surface whilst keeping the watch adequately tight in place on the diver's wrist at depth. NATO Straps. NATO watch straps, also known as "NATO Straps", were developed by the UK Ministry of Defence (MoD) for wartime usage (DefStan 66-47). The colour of the nylon ribbon (20 mm wide) shall be to BS 4800 card number 3, reference 18B25, colour grey. It is a one piece strap slid through the spring bars of the watch case and then slid into the appropriate notch, and then folded back to secure excess strap and prevented from  sticking out of the main watch strap portion. The strap has been used in James Bond movies. The Zulu watch strap and the NATO watch strap are both typically made of nylon. Bund straps, Perlon straps, Marine Nationale straps, Zulu straps, and NATO straps go completely around the wrist, including behind the case. Other wrist strap styles allow the back of the watch case to directly contact the skin.