Mod boxes are one of the rare items in wooden chests. When you open one of these boxes you will will receive one of the modded items available from the pool based on the researches you have already unlocked with your knowledge stars.

The items that can drop in order from common to rare are:

Drawers

Storage upgrade template
Void Upgrade
Iron Storage Upgrade
Gold Storage Upgrade
Diamond Storage Upgrade
Obsidian Storage Upgrade
Framed Compacting Drawer
Framed Drawer controller
Emerald Storage Upgrade

Refined Storage

Speed Upgrade
1k Storage Disk
Stack Upgrade
4k Storage Disk
External Storage
Disk Drive, Grid
16k Storage Disk, Crafting Grid
64k Storage Disk

Applied Energistics

Fluix Smart Dense Cable
1k Storage cell
Speed Card
4k Storage disk
16k Storage Disk
Storage bus
Drive
Terminal
Crafting Terminal
64k Storage Disk

Powah

Furnator Starter
Solar Panel Starter
Thermo Generator Basic
Furnator Hardened
Solar Panel Hardened
Thermo Generator Basic
Furnator Blazing
Solar Panel Blazing
Thermo Generator Blazing
Energy Cell Blazing
Ender Cell Hardened
Energizing rod Niotic
Furnator Spirited
Thermo Generator Niotic
Energy Cell Spirited

Modular Routers

Speed upgrade
Stack Upgrade
Blank Module
Modular Router

Iron Furnaces

Iron Furnace
Gold Furnace
Diamond Furnace
Emerald Furnace
Obsidian Furnace
Netherite Furnace
Rainbow Furnace

Thermal Dynamos

Stirling
Compression
Magmatic
Lapidary
Numismatic
Disenchantment
Gourmand

(All dynamos have a equal chance of dropping)

Thermal Expansion

Device Nullifier
Aqueous Acuumulator
Aquatic Entangler
Batch Composter
Sawmill
Blast Chiller
Vaccum
Igneous Extruder
Hardened Integral Component
Reinforced Integral Component
Resonant Integral Component

Mekanism Generators

Heat Generator
Solar Generator
Bio Generator
Advances Solar Generator
Gas Burning Generator
Wind Generator

Create

Gearbox
Depot
Mechanical Bearing
Water Wheel
Large Water Wheel
Blaze Burner
Mechanical Arm
Cart Assembler

Mekanism

Speed Upgrade
Energy Upgrade
Basic Energy Cube
Basic Tier Installer
Advanced Tier Installer
Advanced Energy Cube
Elite Tier Installer
Elite Energy Cube

Botania

Black Lotus
Gourmaryllis
Rosa Arcana
Overgrowth Seed
Munchdew
Entropinyum
Kekimurus
Agricarnation
Marimorphosis
Bellethorn
Exoflame
Orechid
Loonium

Easy Villagers

Trader
Farmer
Iron Farm
Autotrader