Here's a set of simple low poly taped cardboard boxes. Here's why you should check them out:

• There's 14 boxes total, various shapes and sizes
• They're not just cubes: almost each box has it's own little skews and bends that are never obnoxious, but will contribute to your ultimate low poly cardboard box experience!
• They're literally low poly: elegant 512 vertices total
• They're game ready - you can simply drop them in the Unity or UE and start using them right away. You might want to set the materials first though - they're models, not asset prefabs.
• You can use them for prototyping, props for actual scene building or as main actors
• Original .blend files included, meaning you can edit and dissect them any way you want
• Every box has realistic size, the .fbx transform applied so the model doesn't rotate when imported to Unity
• Every box is named after it's dimensions in millimeters

If you're interested in openable version, you can find it here:

https://www.cgtrader.com/3d-models/various/various-models/low-poly-openable-cardboard-box-pack