Download Sci-Fi Tanks FREE Unity. 

This pack contains 6 different sci-if tank models and 2 ammunition types. Each model comes with LOD group prefab models. Textures contain diffuse, spec (in the alpha of diffuse), luminosity and normal maps.

Check out the Price on Unity Asset Store: https://assetstore.unity.com/packages/3d/vehicles/land/sci-fi-tanks-12998