Slot parts provide extra boost to your Truck's power. Every Truck has some amount of Slots inside it's Upgrades. The amount of Slots is determined by your Truck's Stars and Tier. Slot Parts are divided by rarity, manufacturer and part upgrade type.

You can find all your Slot Parts inside the Inventory. To get there tap the Inventory icon in the main menu. It's located at the right side of the screen.

The parts are sorted by Manufacturer, Part Type and Rarity.