This mod allows you to upgrade your shulker boxes to hold even more items.
Upgrades can be done in a crafting table or by right clicking in the world with an upgrade item.
Each tier has variants for each dye color.
copper (holds 45 stacks)
iron (holds 54 stacks)
gold (holds 81 stacks)
diamond (holds 108 stacks)
obsidian (explosion proof, holds 108 stacks)
crystal (transparent, holds 108 stacks)