Probably the most space efficient airtight (waterproof) box for 12 spools and some desiccant - "Ezy Storage 32L/33.8qt Waterproof tote". Only about 1/8" space on top remains once lid is closed :
Ezy Storage - Water-Proof Storage that keeps everything protected. Life Sorted with Ezy Storage 👌🏻 Available at Bunnings #ezystorage #gardenstorage #garage #gardenequipment #bunnings #ezyhacks #outdoor #organization #organized #storagesolutions ...