I use qubies trays to freeze and then in dated ziplock bags stored in a large containers (to keep ebm together). I typically send 90ml bottles. I may need to top up fresh ebm bottles and adding 30ml at a time works here so I may be slightly over 90ml but DS2 doesn't mind (he's 9mths atm and has 2-3 bottles a day at childcare 7:30am-ish to 5pm-ish)