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Fun fact: current gear actually gives stats to every member of your party, the ones who do not match only get half the Effect. So even if you use Olivia that 2* Flying Bracelet you got from EX Rosa at level 3 will give everyone the same bonuses that a 1* level 3 Rock Bracelet would only give to Olivia.
Another thing, notice how the gear description says "some gear is only for designated synch pairs". Meaning that later on we will get Gear that applies for more than one type or gear that is designes only work for a single specific single synch pair.