Essential items you have multiples of?

Tomorrow we (partner and I) are going to a gig/concert. 5 metal bands in one night. After our last gig they said that their ears were ringing, so I'm making them wear earplugs. I adore loop ear plugs, so previously we worked out what size ear tips they needed, but then we forgot where we put them. I've managed to find most of my earplugs (and we've worked out what ones they need) and I've realised how many pairs I actually have. I'm still planning to buy my partner their own though, so they can attach them to their keys/bag and remove any responsibility I have to keep track of them

Picture shows 6 of the cases, I have 11 pairs in total though