Diving watch on a 4-ring Zulu style strap made of ballistic nylon fabric, derived from the UK MOD's "Nato" strap design.
Ballistic nylon is a thick, tough, synthetic nylonfabric used for a variety of applications. Ballistic nylon was originally developed by the DuPont corporation as a material for flak jackets to be worn by World War II airmen. The term ballistic nylon takes its name from the fact that it was intended to protect its wearers from flying debris and fragmentation caused by bullet or artillery shell impacts. It was not an effective defense against most pistol or rifle rounds (ballistic nylon has been replaced by Kevlar and other, more effective, bullet resistant fabrics for these cases) let alone the heavy 20mm and 30mm autocannons Axis fighters were often armed with.
Modern applications of ballistic nylon include luggage, cave packs, tool belts, police duty belts, watchstraps, motorcycle jackets, skin-on-frame kayaks, and Horseware Rambo turnout blankets.
The original specification for ballistic nylon was an 18 ounce nylon fabric made from 1050 denier high tenacity nylon yarn in a 2x2 basketweave. Today the term is often used to refer to any nylon fabric that is made with a "ballistic weave", typically a 2x2 or 2x3 basketweave. It can be woven from nylon yarns of various denier such as 840 denier and 1680 denier. Denier refers to the weight, not the strength, of the fabric. Laboratory tests have been run and the double weave 1050 denier fabric is the strongest and most durable fabric for its denier weight level. The 1680 denier looks very similar to the 1050 when it is new, but it is actually not as strong as double weave 1050 denier and gets fuzzy as it wears. As it resists abrasion and tearing, ballistic nylon is typically used for luggage and in the bottom of bags made of a lighter nylon or other fabric. Ballistic nylon is hard to dye, so it is often found in black or similar dark colors.