I keep my phone, inhaler and a pocket pack of tissues in it, plus a pair of lighter lenses for my sunglasses. I can also fit a couple of packets of gu.

I use my seat bag for keys, jimi wallet, teeny bottle of hand sanitizer, tampon, spare tube, tire levers, band aids, mini tool, and more gu. Plus my cleat covers if I need them.

I hate having things in my pockets when it's hot, so I generally only keep the chapstick there, and maybe more gu if I need it for a long ride. My pump is on my frame next to the water bottle.