If you intend to mess up your timelines good and proper, so that either fantasy characters find themselves in the present day (either 'real world' or the future self of their own campaign setting brought forward in time) or a few modern people somehow end up with at least some of their kit in an alternate fantasy past, this might be of use to you. (And it does happen, I ran a modern game in which the characters ended up scampering around Conan the Barbarian's world, being transported from 20th century Miami... but that's another story!)

Anyway, what we have here is the sort of kit a modern SWAT-team trooper might have: two types of ballistic vest, ballistic armour, ceramic armour and a couple of riot shields. Who knows where they might turn up? And be quite puzzling to your average fantasy character, to whom armour means leather and metal, and it keeps swords and arrows away from your person, not bullets. Each item has been carefully considered from the standpoint of the Pathfinder ruleset, and statistics assigned. It might have benefited from a little more consideration as to what mediaeval weaponry will do to your 'bullet-proof vest' - most of us have a fair idea of how well it protects against firearms but less concept of what would happen if someone clobbered you with a bastard sword when wearing one.

That aside, get this if you are planning a cross-over, or indeed are using the Pathfinder ruleset in a modern setting.