When the batter hits the baseball into the cage, the ball has a given amount of energy, in the form of inertia. When the ball hits the net, it pushes back on the tether lines at that given point. The tethers extend from one side of the frame to the other, dispersing the energy from the point of impact over a much wider area. This energy is dispersed further as the tethers are interlaced or, in this case, woven.
When the ball pushes on a horizontal length of the woven tether, that tether pulls on every interlaced vertical tether. These tethers, in turn, pull on all the connected horizontal tethers. The entire net works to absorb the ball's inertial energy.
Bullet-resistant material has a similar structure to that of a batting cage net. Long strands of interlaced fiber form a dense net. Of course, bullets travel at much greater speed than a batted baseball. Therefore, the bullet-resistant "net" needs to be made from materials of much greater strength.
There are different types of ballistic materials: Kevlar, Spectra, and Goldflex, just to name a few. Each has its own special ballistic properties that let it perform certain functions better than others. "That's why you see so many hybrid vests, as we're trying to achieve the best of all worlds on those specific functions," says Olsen.
The ballistic materials all work together in combination to create what's called a ballistic package. This is just a fancy name for all the layers that make up each panel in the vest.